I was just thinking this yesterday. In the early '90s in Seattle, I wasn't really buying and selling too much, just had a CB550 that I kept. Switched out bars, tuned it up, all stuff I could get at the dealer (or Bent Bike in Lynnwood, or the Chrome Spoke in Tacoma). Moved to AZ in 1997, and by that time I had started buying and fixing up and occasionally selling -- great yard here (Bob's), the yard in Rye was still operable and reasonable, and I know someone who has about 50 bikes in his backyard (a former racer from the '50s) that I could pick over. But 1997 was also when I got on Ebay, and that changed everything. Not only are (many) parts easily found, they're usually somewhat reasonably priced or they don't sell. Then along came forums -- usually cheaper still, easier to deal with, etc. It's definitely made wrenching on old bikes easier.
That being said, I know where all the 350F and 400F carcasses are at Bob's, and heading there to roam around the acres of bikes is a joy the internet simply can't replace...