Bum-luck, it's easy to think that the yester-year hunters (early 1970s and before) had all the luck, virgin sites, easy finds, etc.... But believe it or not, they hey-day of easy-pickens and such were probably the later '70s into the early '80s. Because machine's capable of finding single coins in the '60s were quite crude, hard to use, lacked depth, didn't work in minerals, etc.... So they too struggled for their finds. Unless they were simply in an utterly easy spot (underneath ferris wheels, or right in front of consession stands, etc...)
If you ever talk to guys who coin/relic hunted in the 1960s, they would tell you that even though they might have hunted admittely virgin ghost-towns, they're "take" for the day's hunt might have been only two old coins, for example. Flash forward to the early TR era (early 1970s, with machines like the 77b), and yes, things got better, and again, their "take" for the day hunting the same areas, might be 2 more old coins. Flash forward to the mid to late 70s with TR disc, VLF-all-metal, etc... And again, yes, they'd farm out a few more coins from the same ghost town patch! Flash forward to motion disc era of the later '70s/early '80s, and they'd get another few from the SAME patches. And so forth, and so on, up to the present So you see, even though parks and ghost towns were virgin in the early days, it's all relative to the machine's ability.
I too heard stories from my city, of a fellow who, in '64 -ish appears to have been the first to ever detect some school yards here (blt. 1920's). And yes, it was all silver then, and yes, he found a lot. But in retrospect, it was all mercs and roosies at probably no more than 2" deep. A barber would have been a REALLY good day, and seateds were only what dreams were made of. Contrast to today, nearly 50 years later, and a simple look at the finds forums shows that we're still finding seateds, barbers, etc.... simply because we can go so much deeper now. I started in the mid 1970s, and never even found my first seated till the early 1980s (on account of the older TR all-metal and TR disc. were so slow and cumbersome, and also that we simply didn't have the mind-set and patience for exotic things like demolition site hunting, ruins hunting, etc...). Now it's no big deal to find spanish reales, seateds, etc.... when logic might *seem* to dictate that those very objects were *easier* in the early days. They weren't.