They do it to disguise the cost. When the first leaf came out the battery was the majority of the cost of the car.. everything that was added on to make it a 'car' was cheap by comparison. So they added frills to get people to pay that much.. and it worked.
Even now, when batteries are considerably cleaner, they're a decent part of the cost - everyone wants a car that can do 300 miles.. that dictates a certain size and weight (given current energy densities) and the companies have to build a car around that.
Effectively if you made a kirkland car with few features it'd cost almost as much as the current EV crop and nobody would buy one to the lack of features. About cheapest so far is the MG ZS, and that's a £30k car. The £15-20k runabout that everyone wants just isn't feasable without compromising range beyond what most would accept.