Okay, so I can see Sebastian taking a look at all of Ciel's friends and thinking "dang, all of young master's friends are so nice and cuddly to their servants. Why can't I have that." And it's true, Alois adores Claude, Hope loves Rosalyn, Soma would probably die for Agni cause they're best friends.

So later he just goes up to the boy and demands love and cuddles and Ciel's just like "...no."