Restaurants, car dealerships, spas and hair salons, construction, plumbers and electricians, doctors and lawyers.

What you are saying is that services can be provided by small companies.

Fair enough.

But we still can see consolidation there.

Starbucks uses a tactic known as ‘clustering’. They’ll build several cafes right in the same area to obliterate competition. This costs a lot of money, but they can afford it... They even use a strategy called ‘predatory real estate’. They pay more than market rate rents to keep competitors out of a location. 

Even in some of the sectors you list - like automotive manufacturing - we haven't seen much net consolidation. We haven't seen a lot of new entrants, but's it's not like the number of car manufacturers is rapidly decreasing either. It's at an equilibrium, and that equilibrium has a lot more than just one company - which is not something you'd see if economic forces generally favored consolidation.

The American automotive market consolidated from more than 250 manufacturers in 1909 to fewer than 50 by 1930. How many companies are there now?

One more example:

At the end of 1985 there were 18,000 banks in the United States. By 2007, this had been reduced to just 8,534, and since then has dropped further. Today, the ten largest U.S. financial institutions own more than 50% of total financial assets.