Because it gets so much use and abuse!Why do you want to reinforce the crotch?
A long time ago, in a galaxy, far, far away... I bought the suit used and it was a custom cut for the orginal owner. The fit in the legs was OK, but not ideal, so the seams in the crotch get a lot of stress when I get my frog kick going.
Too late for the pockets- I squirted some silicone in there and they look "better"