A few parts:

• Ads create common knowledge (as RamblinDash's answer points out)
• Creation of common knowledge is the main bottleneck to creating or moving Schelling points
• Most social symbols/signals of group identity or role identity are Schelling points

As an example, let's consider an oversimplified scenario with two social identities: the MBA types, and the artsy counterculture types. The MBA types want to signal that they're MBA types, definitely not artsy counterculture types. The artsy counterculture types want to signal they're artsy counterculture types, not MBA types. So this is a pure cooperative game: everyone wants clear signals, and everyone is incentivized to use those signals honestly.

But that still leaves a degree of freedom in which symbols signal which group membership. In our world, converse hightops signal artsy counterculture, while MBA types debate the relative merits of oxfords vs brogues. But one could easily (and somewhat amusingly) imagine a different world in which the middle managers wear hightops, and the artsy types debate oxfords vs brogues. The choice of which symbols signal which things is a Schelling problem: everyone wants to coordinate on the choice of symbolic meaning.

Now enter the Converse marketing team. The main thing they care about is that their brand have some strong group identity signal, so that there's some group of people who will buy their overpriced sneakers. Early on, their customer base accidentally happens to have relatively few MBA types, so they lean into that and launch a marketing campaign to establish common knowledge that converse hightops signal artsy counterculture. Their product becomes a profitable part of the symbolic meaning Schelling point.

Notably: at this point, the association between converse hightops and artsy counterculture group membership becomes a real feature of the world; converse hightops have real predictive power about the social behavior of people who wear them (and their friends). The ads aren't just manipulating people into buying the product; the ads helped to create a real predictive feature in the environment. So it would be epistemically suboptimal to be "immune to" the outputs of the advertising.

One thing you might be missing, and the reason that widely-viewed events are so valuable as ad space, is that one function of ads can be to create common knowledge among the audience of how other people might see the product.

For example, Corona beer has a beach vibe. They don't just want you to know that it has a beach vibe, they want you to know that other people know that it has a beach vibe. That way, if you are going to a party and want to bring something that has a beach vibe, you'll reach for Corona because you want to be seen by others as bringing the beach vibe. This is why ads on widely-viewed broadcasts like sports games disproportionately (tho not exclusively) focus on products that are consumed socially or in public rather than privately.

Ads are not just about "manipulate people into buying something they wouldn't normally want". Ads are also about "informing people about something they would want, if they only knew that it exist", which is the most benign form of advertisement. 

And, critically, ads are about building brand familiarity. Which is the easy-to-overlook aspect I'm going to focus on.

Imagine if you wanted a soft carbonated drink, and the three options at the nearest shop were: Oh Cola Soda, Coca-Cola and Penny's Purple Drink. The price difference is, to you, negligible. You're only willing to spend up to 5 seconds on the buying decision. With that, which one would you buy?

It's probably Coca-Cola. You are familiar with Coca-Cola, it's a known quantity, and you don't hate the taste. The rest of the shelf looks like some strange off-brand drinks you've never heard of - which makes buying them a gamble. And why do you find yourself in a world where you're more familiar with Coca-Cola than with the other two? Because someone spent literal billions a year on advertisement to make sure that anyone in the US, young or old, knows that Coca-Cola is a thing.

By spending money on ads, the Coca-Cola Company created the familiarity - which then served as a little nudge in millions of little buying decisions that happen all across the country. Millions of people would try Coca-Cola before they try any other soda. And millions of people who try Coca-Cola would like it enough to prefer it slightly over "unknown unfamiliar soda" for the rest of their lives. Which makes it all worth it.

This post here might change your perspective on the purpose of advertising 

https://meltingasphalt.com/ads-dont-work-that-way/

The idea that advertising needs to be strongly persuasive to work is a deeply embedded myth based on a misunderstanding of consumer dynamics. It instead works as a kind of ‘nudge’ for consumers in a particular direction.

In practice, most consumers are not 100% loyal to a particular brand so they don’t need to be strongly persuaded to move to a different brand. They typically have a repertoire of safe products that they’re cycling through based on which price promotions are available that week etc.. the goal is to ‘nudge’ them to buy your product somewhat more often within that repertoire, reinforce your products place in the repertoire and potentially get customers to trial it in their repertoire. 

See the paper here and the relevant quote which puts it much more eloquently than I can:

There is instead scope for advertising to 

(1) reinforce your brand's customers' existing propensities to buy it as one of several, 

(2) 'nudge' them to perhaps buy it somewhat more often, and 

(3) get other consumers perhaps to add your brand as an extra or substitute brand to their existing brand repertoire (first usually on a 'trial' basis - 'I might try that' - rather than already strongly convinced or converted)

I think the mere familiarity effect is a big part of what you're missing. For some reason, the way the brain works makes us like things we know. If someone walks into a store and looks at two brands, and they have seen one but not the other somewhere but don't remember where, they will reliably and noticeably prefer the brand they have heard of. The other answers are good too.

The fact that they would not even know the brand or sometimes the product type without the ads? Same goes for not forgetting it : Coca does not need ads to sell but I would believe that long term it would be a bad strategy.