I don't bother with signatures, and have never been asked to sign someone elses log, but I certainly wouldn't laugh at anyone who did ask me. I do however log every dive, even dives in pools for training, and keep records of what weight, air consumption etc. was, but also skills I might have practiced or anything of note. I don't write an essay - just short one line notes and so on. I also use Diving Log 5 which does mean that I can track progress and look at what happened last time.
Tomorrow I'm going back to do a boat dive that I have done four of five times already this year, I will have a look at the previous records before I go. At this site, which is a 4 to 5 metre high wall starting at a depth of about 20metres about a mile off shore, even with GPS finding the start of the wall can be tricky so I always try to keep notes about the topography of the site itself as well to help with finding it again.
Bottom line is a log book can be very useful if you are the sort of person who will look at it and use it, and can be essential if you want to prove experience for courses, but they are not for everyone, and if you are not going to do more courses and don't want to keep one it's an individual choice. But should anyone take the mickey out of another for doing so? - absolutely not.
After all apart from being boorish, if this sort of behaviour went on in the school playground we would call it bullying ! - P