Could be a cultural thing, but can be a smart choice. A smaller dog will enjoy living in an apartment and a "limited" (from a canine view) urban life more than a bigger dog.
They're also easier to entertain, especially because many people don't know how to entertain/exhaust their dogs without getting exhausted themselves. No, you're not supposed to run marathons with your dogs. It's much easier to train them to fetch stuff like frisbees and you can sit in a chair all day for all they care.
My dog has a knee problem so the vet told me to not fetch with him. Fine by me but it makes tiring him out all sorts of tricky. Training him for treibball at the moment as that's one of the few dog sports I've found that doesn't involve quick direction changes or jumping. Fingers crossed he'll take to it.
They're also easier to entertain, especially because many people don't know how to entertain/exhaust their dogs without getting exhausted themselves. No, you're not supposed to run marathons with your dogs. It's much easier to train them to fetch stuff like frisbees and you can sit in a chair all day for all they care.