The obvious reason is that small hatchbacks (B-segment) are more expensive, both in terms of purchase price and in terms of running costs. And that's my point. Manufacturers don't want to make cars that cost almost as much to produce, but are sold for cheaper.

Also, it is easier to park these small cars, but really, what effectively happened is that manufacturers removed the cheap option on gas cars and claim that the replacement is an EV. It isn't, the A-segment was a cheap, city-optimized, single car option, these small EVs are also cheap (for EVs), but city-exclusive, second car options.