Never. For an easy example just remember about shoving your AK preflop against someone that calls with Queens or any lower pair and you hit your ace on board win the pot. Isn't it luck? I mean it's flip (with he's being slight favourite) however you get all the chips. Sure, you made right play so he does. At the end, he's out, it's you continue playing. There's many examples even the worst situations like someone gets into pot with less than 20% of winning, end up makes his hand - takes the pot. Another situation would be like you win allin with AA against opp's KK. We all know we're approximately 82% ahead so it shouldn't be considered ''luck'' if we win, right? But I think in behind of it, we're extremely lucky being have Aces at sametime someone got Kings.
Certainly no one might do it just because of luck however all you need to run good in long period of time, tens of critic spots.