I don't understand how some shops offer those items. Why buy something that you can't use, and the only purpose for said item it to sell it for gold? It would be like buying gold for gold. edit: I meant the treasures.
Do you mean treasure? Shops don't sell those, except Sharl's which only resells items you've sold. If you mean 'items that aren't very good', well then there are many reasons - the items are random, some are better than others, and some that don't appear to be useful actually can be in some circumstances. If you mean 'items you can't use right now' (because you don't have the right races/classes in your party, or enough tokens available), then it's because the shops don't look for that. They just offer a random assortment in a certain level range.
Some people just like collecting things, and since the holiday items are only available for a short period of time, they decided to make all of them available in a special shop, even the treasures.
yes, the treasures. Seems strange, but I guess if people like to collect everything then it makes more sense.
I kept some of the cooler ones for a while, but eventually decided I'd rather have the cash and go admire them at Sharl's if I want. I sort of picture it as less of a shop, and more like the warehouse from the end of the first Indiana Jones movie.
Warning: Skarl clears out his inventory about once a month. And some treasures can only be obtained once (White Star Diamond and Jewel Of Alet Zhav).