Oh boy, "rock-used-to-be-so-much-better" thread #87,563. OK, I'll play.
In the '60s and '70s, rock bands had a huge ready-made audience (thanks to the Baby Boom--birth rates have been much lower for a long time now) to buy their albums and tickets to their concerts.
In the '60s and '70s, people had far fewer entertainment choices--no internet, no online games, no movies you could watch at home, no shows could be recorded, only three channels plus some snowy UHF instead of 500+.
In the 60s and '70s, concert tickets were cheap!
In the '60s and '70s, record companies served as gatekeepers, so only a limited number of artists could really have their music distributed--so not only did you have a far bigger audience, you had far less competition.
In the '60s and '70s, record companies lavishly supported their artists with massive promotions and huge recording budgets. If Steely Dan started today, no way could they afford to hire five full bands worth of the best studio musicians in the world to record a single track.
In the '60s and '70s, people had to pay for your recordings, so you made a lot more money.
In the '60s and '70s, there was no social media to track every single move a musician made--far fewer "sins" were exposed, and pictures and video were far more rare. Thus rock stars seemed more mystical and bigger-than-life. Today, if a famous musician goes out to the grocery store in sweats and a ballcap, 10 people are going to snap a picture on their phones before the person is 5 steps from their car.
The people haven't changed, just their circumstances.