This would break the game and all the story behind it. It's like asking NBA 2K games to add snowmobiles next year, because wouldn't it be more fun and exciting to play basketball on snowmobiles? You walk everywhere for a reason, the freaking nuclear war happened and everything went to shit. Even if they managed to somehow make vehicles, where would they get the fuel for them? Would they be the generation, that figured out how to power cars without using gasoline?
I thought all the cars in fallout had little nuclear reactors in them or something