I don't sleeve mine. It would make sense if you were shuffling a deck of cards, since cards get hacked to pieces if you don't have sleeves in that context, but there's not a lot of opportunity to really damage your cards since they remain in a pile or your book most of the time. Plus, I like the continuity of the art in the cards in relation to the game board without technicolored sleeves breaking some of the immersion factor.
In either case, I don't make a habit of drinking or eating at the table while playing anyway. Even if I used sleeves like I do in other games, I think it's kind of inconsiderate to leave non-bottle drinks on the table. It's like subtely acting like you don't care about the worth other players put into their belongings.