Why were sam and lilith going to have sex?

Question

In the television series, Supernatural, S04E18, Why were Sam and Lilith going to have sex at the first place at all?

If Sam was going to have a contract with Lilith, then that would require just a kiss.

Answer 1

From Supernatural Wiki

Lilith is able to make deals herself and is bound by the same rules as a Crossroads Demon in making them, however, she claims a deal with her will take a sexual act instead of a kiss, but this may simply be her preference.

As far as I remember, she explicitly tells Sam that this deal needs to be consummated instead of the usual seal-the-deal kiss. But then again, I think she was just toying with the handsome man.