I am a road rider that started in the late 1970's and the biggest change is the attitude of drivers in the US. As bad as it is now, it was orders of magnitude worse back then. Now getting yelled at by a driver is extremely uncommon (at least for me). Back then it happened daily and you were much more likely to get "buzzed" or have garbage thrown at you.
Another change is the demographics of the riders. Back then there were very few riders aged 40 or older and if you found one it was likely that they had a foriegn accent. Now there are huge numbers of them.