I was a fairly early adopter of 700c clinchers. Before that I had used the 27x1" tires on my racing bike for training. They were a bit slower than tubulars but a lot cheaper. It was nice when 700c x 25mm became available because I didn't have to worry about adjusting the brakes when changing wheels. Otoh, I have a couple of scars on the back of my head because I wasn't too careful about the chain/freewheel matching up.
When I built my touring bike in 1980, I put 27x1 1/4" tires on it because you need good availability of tires while on tour. It's pretty funny how wrong about that I was. I wasn't paying attention to the bike industry when they decided that 27" was passé, but by the mid-'90s it was definitely all over.