This is an entirely different argument, but if you ask me (and many other longtime ARAM players), all champs should be available in ARAM to begin with. In kind of a stubborn display of optimism over that, I'm not inclined to accept that as the sole reason to allow even simple, no-refund content deletion from an account.
And really, I just don't feel sorry for people who spend their IP or RP irresponsibly. Try a champion before you buy them. Or just accept that you permanently have them after you buy them. If you care about ARAM, accept that buying them will put them into your ARAM pool. And then deal with it.
I'm okay with the current refunds existing. And I'm okay with them being limited to 3 for the lifetime of the account. They're for situations where you go buy a skin, take it in game, and decide that you're truly dissatisfied with the skin for one reason or another. They should be used more carefully than 'oh, I bought this guy on a whim and didn't like him'.