Some took their .30-06, some took their .30-30. their .300 savage, even .25-35's.
And most "what caliber should I get threads" usually end up including the .30-06, still being one of the most popular rounds out there. The .30-30 is still often used, the .300 Savage was supplanted by the .308Win but is slowly making a comeback [Savage and T/C both have production rifles chambered for it]. You talk of a circle, and yes, I think its slowly coming back down. Sure, you'll always have people talking about magnums, long distance shots, etc.
Part of it, I really think though, is just the appeal and the fun that all the other offerings bring. With the Depression Era survivors, being conservative about ammunition was just something ingrained in them. These days, we go out to the range all year round to have fun, plinking away at varying targets. We often shoot, not just to put meat on the table, but for fun. Part of that fun though, is challenging ones self with longer shots and bigger loads.
As a side note, don't fool yourself, if our grandfathers had been able to get ahold of some of the camo we have these days, they probably would have used it.
Personally, I'm in my 20's...my one hunting rifle is a .270 Win. Bought it because it was all the gun I need for what I want to hunt. And honestly, among my shooting friends, all in their 20's, all of them respect the .270Win as a good round.
If I get into bear and moose, I may move to something like a 300 WSM, but the one caliber I have wanted for about a year now....the old 300 Savage.
Cheers and happy hunting!