It really depends on how they're used. I've been in groups that were against character sheets and almost every time there were people accidentally creating the same characters just different names and genders or pushing their characters toward similar character arcs without realizing it until we got the "multiple characters with two souls, one body oh crap this was supposed to be my thing" happening. Also, going through 2,053 posts just to find a character's eye color (when even the rper forgot their own character's eye color) isn't my idea of fun. I consider them a starting point with a little bit of a direction. Sometimes things change. That's okay. If I'm running the rp, I usually keep a copy of the rp, copies of the character sheets posted by the players, updated character sheets I keep that include observations and relationship arcs, and whatever notes I need.