I haven't shopped Christmas, but I have done gas stations on Thanksgiving, some on major travel corridors. And yes, the lines were terrible and the forecourts had lines at the pumps. And yes, the pay was irresistable. (This was in the Martiz days.) I'm not single any more, so no more holiday shops.
More recently, I did some shops on Black Friday, and some ended up getting excluded because that turned out to be a blackout date. Oh well, picked them up again for double the pay a couple weeks later. But the main problem with holiday shopping, even if allowed, is a lot of places will be closed without saying so on the website, and you won't be paid anything.