Those famous words.

I can think of lots of reasons:-

I want to keep her hanging, and want me more...she'll be **** well trying to please me more now and make me fall in love with her.. reverse physcology for personal gain.

I just want sex, your horny in bed, your a nice woman, there are feelings but.....

I may have "thought" i was in love with you but i just don't feel that way, i of course do love you, "as a friend" with a bit more of a bond, connection but....

Let's not hurt her feelings but lets not get her hopes up to high, **** women with emotions is too hard to handle, i'm having fun.....

No, i can't think of any more, but everyone else feel free to add....