More routes got done for one thing. Nowadays, an R rating scares everyone off. I think lots more people did R-rated routes before anyone knew the routes were R-rated. Folks went up, and if it was scary, maybe they backed off but maybe not. I don't think it was more dangerous, but it was more common for people to back off and come back, sometimes multiple times, before eventually succeeding.
The flip side, perhaps illustrated by the Ruby Saturday discussion, is that a misapplied G rating lures people onto climbs that they may genuinely not be ready to deal with, and the rating puts them in a frame of mind that may not be conducive to effective reality-testing. ("It's G-rated, so there's gotta be some good pro up ahead even though I don't see where it could be...")
In general, the idea that any route could, in modern terms, be R-rated meant one approached climbs with a different mental outlook, one that was at once more cautious but also better primed for the unexpected.