Here's the reason drop outs are so high>>>
People come in wanting to learn cool subs and "jiu jitsu" like they see in the UFC.
People, no matter what their experience in grappling do NOT like to get their asses handed to them in "hard" rolling that takes place after instruction. You have guys that maybe have been there a couple of months just mauling these new comers and "practicing" up on their neck cranks and chokes.
After you leave a class in which you were choked out a couple of times and your arm is sore from kimuras and your ankles are sore from ankle locks you didn't see coming and that were cranked to hard by newbies (and advanced players as well), you do NOT have a great motivation in going back. This is NOT fun for you. You want to learn subs and have some fun, not necessarily roll at 100% speed, which is almost always what is going on.
You should be learning techniques and subs for a long time before you start rolling at 100%. You should be working on conditioning and stretching for a while to before a new guy is allowed to roll full speed. Yet instructors and people in the class seem to use the new guy to practice "chain" submissions and exotic subs on. This leaves the new guy confused and bewildered.
That's a bunch of BS when guys say "oh, that's how you learn".....total bullshit! People want to practice their own technique, and rarely do you see them taking all kinds of time explaining just how they exectuted that reverse heel hook.
Bottom line....people like to use new guys as practice dummies, and instructors should be the first ones to identify this and regulate it.