I got my papers in 1953 - still have the cotton helmet and Gosport tube - and did my multi-engine on a Gemini a couple of years later. From this you will deduce that I'm an old fart but this does perhaps allow me a broader perspective.
In my estimation, people have dropped off simply because flying is very far from being as much fun as it once was. Since the greatest prerequisite for doing anything is to enjoy doing it, there must be a simple correlation between fun and participation. And the two party poopers here are beauracracy and technical complexity. I suspect this view is supported by the degree of fun derived from private flying to be in direct proportion to the age of the aircraft - pilots of pre-war machines have a whale of a time.
In the old days - here he goes again! - if the engine started and the weather was acceptable, you waved away the chocks and went. A friend recently trying to visit me at my local strip had to cancel as the transponder was inop and this evidently was a bigger deal than just not being able to squawk because it interfaced with TCAS and the MFD and goodness knows what other gizmos in the alphabet soup, the absence of which did not prevent the a/c from flying.
To be frank, if I was still involved in private flying, I would jack it in too - I just cannot see that the restrictions of airspace controls and attendant reporting, glass panels and all the legal mumbo-jumbo now drowning what used to be a simple pursuit, is worth the candle.
I mean, can you imagine carrying enough crystals to cover three decimal places?
But I agree with Guppy's view that these boards do offer a useful, albeit vicarious, contact with the remnants of a world with which a lot of us were once familiar. Yes, I too have fond memories of holed and cigarette-burned flying club sofas. I also remember, but with less affection, the Brylcreem-lined leather flying helmets hung outside the CFI's office.
Gippo.