If you can roll three 18's, mind you. I couldn't do that in 10,000 rolls.
That was not the premise tho. So the point still stands. Also: a single 18 is pretty damn great, because with the standard-array/point-buy the best value you can assign is a 15. Add to that a +2 from race and you have nice fat 20 on level 1. That is you mainstat being done. No more opportunity costs from that. If you have a SAD character like a Rogue, you have a pretty huge edge.
Rolling dice is better than standard array in around 56% of the cases. So you don't need to roll too much just to get an advantage. There is a reason why things like the AL don't allow for stats rolling.
