I think for me it is that other games have too much down time. I've been doing a full playthrough of the Witcher series. W1 was painful to play. There is so much running around and accomplishing very little for so much leg work. W2 has been better, but it still has a lot of down time and dice games that are so hard to win compared to W1.

With league, you wait in queue and champ select and in champ select you still have decisions to make so it keeps you engaged or you can pick and walk away during loading too. Doesn't require you to be there. Then as soon as the game starts you get into the action.

Other games have a hard time keeping my attention for that reason.