As you say, the biggest issue is not playing ready golf and players being unrealistic about their abilities.
Standing on a tee box and watching the group ahead of you wait to hit, while another guy sits in the cart. Then the guy hits, climbs into the cart and they drive over to the other guys ball to hit. Then they're on the green and one guy has to hit out of a bunker. So he hits, then everyone waits while he rakes the bunker, marks his ball and putts because he's still furthest from the hole. The next hole is a par 5 and even though the guy drove it 220, he's going to wait for the group ahead to clear the green so he can try to hit a 230 yd 3WD from the rough - because ya know, that time in Myrtle he pulled it off - only he duffs it, then waits for everyone else to hit, and he has to hit again. Then the next hole is a par 3 and instead of letting the guys waiting on the box play through, they pour over their $5 Nassau and re-mark their third putt for double bogey. They then stop with the drink cart girl before the next tee.
Pace of play for amateur golf has very, very little to do with professionals influence. It's more about ignorance and ego.