I just don't get it

I went to the gun shop to pick up some defensive ammo for my new glock 30sf and all they had were some 165gr or 185gr choices. What on earth is the point? Why wouldn't I just get a .40 if I was interested in those weights? When I asked if he had any 230gr hollow points of any brand/variety, he looked at me like I was stupid and said "don't get many requests for those.." Really?