I believe when you see someone regularly, you are both able to evolve and develop. Fantasies are expanded upon and a friendship is formed.
The downside is going too far. Over the years, a couple of ladies have cast me aside with poorly-planned lies/ exit strategy.
My take is that the fantasy side of things was wierding her out and (in the second case) I was getting too much fantasy for the base rate on an R&T.