For me personally I find very few whores that are worth dfk-ing. I don't smoke, have I think quite a sensitive palate, and find most whores who dfk offend my taste buds.
It's like fanny munching. A well-kept, reasonably clean fanny can have many delicious tastes. An over-cleaned one tastes of fuck all or, even worse, soap and flavoured gel. If it looks very desirable I'll give it some oral attention if it isn't minging but few go in the top ten taste bracket.
The mouth both retains a lot of flavours -- especially the area around the back teeth -- and the salivary glands are affected by so many things that can affect the taste of a dfk, from lifestyle, diet, mental outlook, age, hormone levels, and whether the girl finds you the slightest bit attractive -- something that sets up a hormonal response circuit. As most prossies eat junk, have no life, are only motivated by money and make a living by sucking and often kissing any old bastard, they are hardly likely to have the tastiest mouth flora. So generally I couldn't give a fuck about more than a few kisses and a bit of tongue to express willingness. I'm there to fuck them, not make love.