Also we're going to be rolling dice in combat, its no different, it could be really kind to someone and be really bad on others.
However, there is
a big, huge, neon difference. If you make an attack roll and fail, you miss that attack. If you survive, you can make another attack.
If you roll for stats and get straight tens, you pretty much suck forever. It's like a save-or-die before you even have saves.
With the attack rolls, your character performs poorly. With rolling for stats, you could well be disallowed from playing your character. It can cordon off being any good at wide ranges of characters, or give you the choice between being any good at anything, or playing the class you want for the character you want, which is an extremely
bad thing, because it makes playing the game and roleplaying enemies of one another.
Rolling for stats may be a tradition, but it's also a very bad rule. Which is why it's not the default anymore for 3.5/4e. If someone chooses
to roll for stats, that's their business, but it ought to be because they chose
to give up that level of control over their character.
And note, I am aware of the array and the point buy in place. I'm just discussing the drawbacks of requiring stat rolls.