Sledding is pretty great:
No lines. You don't have to wait, just go.
Minimal cost. A basic plastic sled costs $15-$20 at a hardware store, and while they wear out pretty quickly it's still less than $5/outing. Aside from that, all you need is standard winter gear (including snowpants).
Close. Around here there are two decent places to sled within a 15min walk, and several within a 15min drive. You can go sledding after work, or as one of several activities on a Saturday.
Good learning curve. There are many hills where all you have to do is sit on your sled, no skill required. As you figure out how to steer, this opens up other hills, and more interesting options for going down existing ones.
Fast. Zooming down a hill is just really fun.
The competing ways to move similarly fast are much more expensive, require more travel, and you spend much more time time waiting around and less actually moving: amusement parks, skiing, etc. I'm not trying to knock those activities, they are definitely fun, but I think sledding more than holds its own here.
This morning the kids and I went with their aunt to a park near our house:
We were there for about an hour and a half, and there were less than ten other people sledding. I'm sure there are more now, since it's a bit later in the day, but still, compared to the number of people in the area I think would enjoy sledding it's surprisingly low.
Why is that? Some guesses:
You have to walk back up the hill. True, but it's good exercise and it beats standing in line.
There isn't any advertising for it, beyond advertising for sleds.
In most places it can't be scheduled. You have to notice that the conditions are right and decide to go, typically on less than a days notice.
We think of it as something for kids. But amusement parks have this too and are still popular with all ages.
In places that have good sledding many times in the winter people think of it as a normal thing, and we get more excited about uncommon activities?
Maybe people don't know where to go? There are sites about the best sledding options, but they aren't great -- some sort of sledding hill review site where people describe hills and give ratings could be nice.
If you're in Boston and have been meaning to give it a try, conditions are good this weekend. I'd be happy to lend you a sled and/or other gear, and give suggestions of places to go!