The basic reasoning is that batteries are still very heavy, and take up a lot of room. In order to have passenger and cargo room (with a lot of heavy batteries), the vehicle needs to have batteries underneath it in a platform configuration, not in the trunk. Since both the Bolt and Model 3 are targeting 'affordability', the bodies can't be built out of aluminum and carbon fiber, so in order to keep overall vehicle weight down, they need to be small.
Put another way, don’t expect the Model E or the Bolt or anything Nissan, Audi or BMW to put out to look like a sized down Model S.
Why? Well a 20% smaller Model S (purely scaled down) means:
1.) Nowhere to put the people. (I have a Cadillac ELR, which lost 1 in of headroom from the Volt for design aesthetics and I barely fit in the front seat now and the back seat is basically non-existent) Remember, this is with a car that has a T-shaped battery and not a skateboard battery)
2.) Wait we have to use steel again to make it inexpensive? That means we aren’t building as big a car or it’ll weigh too much.
3.) 20% smaller car doesn’t mean 20% smaller battery capacity to get the same range. While weight matters, aerodynamics matter a lot more for distance driving. A “smaller” car doesn’t always been less aerodynamic load, especially given how slippery the Model S is today.
Full article here:
http://www.mychevroletvolt.com/why-the- ... chevy-bolt