ARAM afks
Pretty much all of my games there is 1 or 2 people AFK at base and they dont buy their items/leave base until after about 50+ seconds in, then they don't have the homeguard speed buff. That gives enemy team an advantage when there are early skirmishes or just by having brush control; they can fire skillshots from fog of war. You can't see them or target them. This really hurts the team and it's not even reportable. FeelsBadMan.
Edit: What if we made it to where you have only 30s to buy items? I don't see why people queue up for a short game mode like ARAM and leave their computer/laptop. People shouldn't be queuing up if they aren't ready, that's what the initial ready check is for when you accept the match.