I'm also at that post PPL stage where I've seen all the local area, taken friends and family up, and need to 'spread my wings' as it were. Although I've no thought of giving up, I must admit I looked out the window at the glorious weather we're having at the moment, thought about going flying, and though "No, can't be bothered".
It's been said before, but the main thing that disillusions me is the weather. I can't complain because I knew what to expect - I was under no illusion that the basic PPL would be useful as a tool for getting from A to B. It's just that the thought of going beyond the loca area, getting stuck in weather, screwing up everybody else's flying because the aircraft isn't available, having to stay over in a hotel etc. etc. just put me off. I've no shortage of places I'd like to visit and I'll set off to the airfield with a nice 100-mile long line drawn on the map and end up doing stalls and PFL's in the training area yet again.
I think the answer for me will be to fly abroad more. I just got back from 6 days in SW Florida and it was thouroughly(?) enjoyable. STILL managed to miss a whole days flying due to weather though
Next I want to fly in France, Greece etc. etc. but I can't afford it at the moment. Still, it's somthing to look forward to - I lack neither the will nor confidence to do these things so I think it's just a matter of time.
People are right in that the Pprune fly-ins are definatley somthing to look forward to. 5th April is only 7 weeks away
but I can't help but think that the weather might have somthing to say about that day too!
So, in summary, I believe many people must give up because of (a) the weather and (b) the restrictions of hourly aircraft hire. It would be interesting to compare drop-out figures here with other countries.