Spit, like most aspects of fetish play, is relative. A random person spitting on you, would not be enjoyable most likely. For a sub, its an enticement, but it also shows the respect and adoration of a Mistress they have chosen to serve. It can be degrading, but also, a gift of pleasure from someone the subby has seen the Goddess the Domme is, which is a compliment to the Mistress. Submission is not for the weak, it is for those strong enough to experience all the aspects of their persona. Just my thoughts.