While I don't have a problem with rolling stats in of itself, what I don't like is the player problems that it has the potential to bring. Either the people who always seem to have the awesome godlike stats that they rolled at home before the game, or the player who will roll in front of the group but if gets less than godlike stats will pout and have the PC with a death wish which just gets disruptive as he goes through pcs.
As a dm, it just avoids those types of player problems but not having rolled stats.
That's based on my own person experiences. I know not everyone has necessarily seen those types of player issues, but I've seen them enough that I just would rather avoid the potential of those problems in the first place.
I hate rolling stats with such a burning passion, the likes of which cannot be cured with antibiotics. I don't like that you can get high rolls or low rolls, as a DM or as a player. I'm playing a PC in a game where the DM rolled our stats and we all got very good scores. I feel overpowered and had to alter my character concept to suit the rolls. But the alternative was to have a significantly less powerful character in amongst powerful characters, which is even less fun.
Point-buy isn't just about having balanced stats, it's also about being able to craft the character you want as opposed to the character you're stuck with because of a random set of numbers.
I have a weird personal divide: I love rolling my character stats, but the game generally plays better when it's point-buy, so it's what I encourage as a GM.
Random has its place and it's not in stat generation or hit points.