I've never actually noticed cheaters during the time I played the game. If they cheat and matchmaking puts me against them, it just means that me without cheats and them with cheats are equivalent in skill level, so it's a fair and fun game. So I don't see the point in preventing cheats in the first place unless you're at the very top of the ladder, and there's so few people up there that it should be easy to just manually ban the cheaters.
I think a part of it is the difference to losing to something "reasonable" vs "unreasonable."
If you're clearly really bad at the game when we are in a fight with line of sight but somehow you keep picking off my teammates through walls... That's the kind of thing where cheating really starts to get annoying.
You may still be on the same skill level overall, but for specific parts of the game they have super powers, and it just feels ridiculous.
Smurfing is also a real issue because cheaters seem to overlap with trolls that just want everyone else to have a bad time, so they'll spend a bunch of time down ranking, so they can spend a little time giving a lot of players a bad day.
I think a part of it is the difference to losing to something "reasonable" vs "unreasonable."
Yeah, that's understandable. I just don't think there's an equivalent in LoL that would feel particularly unfair. At worst, someone just knows where you are at all times. What do you do with that information? That requires good game knowledge. You can only influence a small portion of the map yourself and teammates tend to like acting independently even if you provide them with extra info.
Smurfing is a bigger problem, but I've found that Riot tends to be very good at gauging your skill level even if you intentionally sandbag. LoL is just one of those game where it's really hard to convincingly pretend to be bad at it.