I'll never forget why I started trimming my pubes.
It was a fairly cold day, so there was some significant shrinkage. I don't remember how or why, but I was getting turned on and started giving it a little rub. All of a sudden, there was this intense pain and I jumped up and ran to the bathroom to examine. Apparently, when it shrunk, some of the hair had weaved over the head. As it started to engorge, it trapped the hair between my head and my jeans. Once I finally started getting up to size, I was pulling the pubs out with my erection. So I started trimming then and there.
Similarly, on the back side... My mom used to buy the really fluffy, girly toilet paper; the kind that leaves lint everywhere when you wipe. Well, I was in the shower one day, washing my crack, when I discovered a lump. I gave it a gentle tug and nothing happened. So, I pulled a little harder and it stayed put. Then I started pulling until it moved... and brought with it a ton of hair. It was a reinforced mud ball, held fast with TP lint and a hair weave. I was so disgusted I started shaving my crack from that day on.
I use a 3-7 blade razor and I've only nicked myself twice as I remember. Once was on the starfish, and BOY DID THAT TICKLE.