we don't really have classes for bitesports, but retention is horribly low for all sorts of reasons. Mostly, it's work, lots of it. if you have a puppy you won't be competing for almost 2 years minimum. Most people want a 6 week course and a certificate and to move on to the next level. You don't get to do that in ipo or ring sports, it's a little more than that.
Next, while most people are rather friendly, our sports have our share of assholes. The ones that forget what it's like to be new and not know anything about how, why or what the hell is going on and treat newbies like dirt. Most are not like that thankfully, but there's always one it seems.
Then we have the dog issue. So many show up with a dog from "somewhere famous" with all these lines they researched and they're very proud, and the dog doesn't have an tenth of what it needs internally to be able to do the sport. When they see everyone else doing things their dog can't do they either quit or try and find someone else to tell them something different. and that works for a while, because that person will keep telling them what they want to hear till the money runs out, then they're gone and soured on the sport forever.
My first club I joined is gone. Nobody is still training from that club other than one person and she is just training for fun, hasn't competed in years. The club after ( I had moved still has the core members that were there when I started with them (about 5 people) and during my 6 years with that club lots of people came and went. I'd say at least 25-30 that stayed for various amounts of time. Of those that came with or after me, Myself and one woman (switched to ring sports) are the only ones I know of currently still training besides the core of 5 members that were there before I started. I still know a lot of those people and they still have dogs, but they don't currently train for anything. Some don't have dogs at all now.
I moved again (and it sucks because I had a **** good trainer for bitework, now I have just me ) and I was with this current club for less than a year and I left. Too much drama in it for me and not enough training. in that year though I can think of at least 8 people that never made it past 6 sessions and they left because it was too much commitment or their dog didn't have enough. Oddly enough I still train dogs for almost everyone that was in that club, just not in the club setting.
I'd say over the years 80% of the people come out for a few sessions or maybe even a few months, but the amount that stay a year or longer and actually compete is much lower. 20% would be generous I think it's probablly closer to 10%