They exist, but usually they are expensive and in-demand areas because... people usually like walkable areas. Its a shame that more suburbs arent designed this way, because it doesnt even cost more money...just more thoughtfulness in how we should design our livable spaces.

Suburbs/car-dependecy is a classic case of "worse is better". Its simpler to build and the worst-case suburban sprawl is tolerable, so it proliferates.