Question on Hextech Permanents

So for the hextech crafting permanent skins, I have noticed you can reroll skin permanents if you don't already own the champion but not if you own the champion. Here is a picture for an example: http://grabilla.com/06802-12fb5965-532e-436c-b425-4d0be07b25a2.html

So I feel for consistencies sake, should we not be required to keep the permanent skin, or should we be given the option to activate the permanent we get for champions we own or re-reroll it? Just doesn't make sense, rarely would I ever reroll a permanent bc that's starting to get wasteful but in the case that I get giant enemy crabgot, I'm never gonna use that ever. (I own butcher urgot and I don't like urgot anyway so yea) But since I was gifted urgot as a joke I have to deal with his skin permanents when rerolling them would genuinely be in my best interest.