The thing is, letting people pick turns off the "Must have the highest possible scores because this is a competition" part of the brain, and turns on the "what will be interesting because there plainly is no competition" part of the brain.
The second is almost globally better.
IMAO this is crap. If it's actually a preference for random or for rolling then why all the fancy dice rolling methods? If people like rolling dice and like random, 3d6 six times in order is fine.
People want higher scores than the 5th edition point buy will let them have, and find that "I want to roll dice" is a fine way to get them.
I'm old school. There are no racial minimums in Men and Magic as best I can recall.
Because, it's more interesting and fun to choose something else, so they do, because once you say "choose anything" then it becomes obvious to most people that 6 scores of 18 is BORING. But people get to play what they want, which is good.