I think a big part of the cause of drop outs, is that flying schools are geared up for training and not for PPL's. At least that is a big part of the problem over here.
When I had completed my PPL my cross wind landing were faultless. I could even impress myself
However as a PPL I was not allowed take a plane if there was a cross wind component anywhere approaching 15kt, even though the a/c has a demonstrated componet of 25kt, unless flying with an instructor! As a result my crosswind landing are now crap!
Same goes for vis....My licence says i can fly in Vis as low as 3km....anything less than 15km and you'd be getting strange looks!! (Not that I'm recommonding 3km vis to anyone!)
Schools apply the same cotton wool approach to PPLs that they apply to students, and this can be very fustrating. Now I'm not saying that they shouldn't be cautious. But if a PPL can demonstrate to an instructor that they are capable of flying safely in given conditions, consistantly, and it's within the liminations of their licence and a/c limits, then they should be allowed.
As an example, I once had to do a currency check on a day when flights were "with an instructor only" due to cross wind. I did very well, had no problems, and the instructor commented something along the line that my cross wind landings were very impressive. So no problem with the sign off, but no flying today with out an instructor!
As a result you become limited to "easy flying days".
Another part of the problem is due to the lack of social scene. It's actually very hard to get to meet other PPL's. My flying budget allows me to fly a 2 hour trip, every second week. Starting and ending in the same place, means that I can never get more than 1 hours flight away, and I soon get very familiar with the area. (Leaving it for 4 weeks would require a currency check, and negate the saving). Now sharing the flight with another PPL would double the distance and make overnight trips more realistic (due to min flying hours). However getting to know other PPL's is difficult. Flight training is not a social activity. You turn up to the airport, go of with an instructor, no one else, and then come back and leave. I've slowly gotten to know some, but it has taken a long time, and I'm sure many others have given up before making those contacts.
The sad thing is that these problems are easily solved. Overly cautious restrictions should be lifted when you have proven your ability (subject to currency checks as necessary), and a better social scene in clubs would help people make contact with like minded people.
I'm luckey to have found a club of PPL's now (rather than a training school). I now have more restrictions on the weather and destinations than I had before, but the club will lift each of those as I get an opportunity to demonstrate to my instructor that I'm capable of handling them. And as I said, over time I got to meet like minded pilots.
However, despite the fact that I love love love to fly, I came very near to giving up due to fustration with the school (post ppl, and not my original school, who were excellent, but were taken over). Only my love of flying made me determined to find somewhere else, somewhere better. I dare say many give up before they find that place geared up for PPLs, not not SPLs.
dp