I've done it several times. Vampire and Werewolves I bought because of CAS/BB though I probably will use them eventually in some future game add them (I do have an idea of an post apocalypse game where everyone but my sim is either a vampire or a werewolf).
Journey to Batuu I bought exclusively for the CAS/BB without any intention of ever playing on Batuu. I don't regret it for a second.
Get to work I bought because I wanted to stores for my sim to visit, not because I wanted to run them. Same for Dine out. I have yet to play full out the Eco Living, though I do use some features in my game and intend to at some point to make full use of the world and gameplay.
In general, if I buy the pack on sale, and I really enjoy some features of the pack, it doesn't really matter to me if I use all of the features. So far the only pack I regret buying is My Wedding Stories.
