In denser areas they do, but honestly most new development malls are looking like that now a days with huge garages and an effort to maximize the developable land. I think Easton in Columbus, OH is a fair example of one of these newer malls with garages, and outside of a big city too way out in the exurbs not too far from cornfields. There are some lots but as the area has been infilling they've been adding garages.
Probably because customers aren’t going to malls for a short trip and taking 5-10 mins extra to park isn’t a big deal compared to them going to a small shop for 5 mins and getting out of there.
I don't know why you've come to that conclusion? I do the exact opposite. I got to malls to buy something specific, but there's no reason to spend anymore time there than necessary. City centres are the opposite.