The first two reasons, to me, feel like excuses to hide the true reason(s) they cheat. I'd wager it varies per person but that many just want to be seen as cool or skilled by having everything or beating everyone. It seems equivalent to people who modify cars to be extremely loud; despite many saying the contrary, they've convinced themselves that people love to hear their loud cars go by.

It could also be the anonymous effect of online games. They don't quite perceive themselves as cheating, really, because they don't know the players and will never know them. It likely feels like NPCs in a video game, for the most part. If there were actually social pressure, like would be in a schoolyard game of football, then far fewer would be willing to risk the social ostracization. But because they are anonymous online, they feel safe and empowered to cheat.