Why are irem-sets not saved the same way as runes and masteries?

I'm sure it happened to all of us at some point. You took a long time to make some neat and useful item-sets and then until one day you realized all of your item sets were gone.

It happens when repairing and it happens with some patches and damn it, it's annoying. After I lost item-sets the 3rd time, I just stopped re-making them and kept core item notes in my own file.

I'm sure it's been brought up before and perhaps even answered, but I think item-sets should at least be preservable, if not account-saved.