It just isn't GFE without some serious tonsil hockey. Like you say it sets the mood and allows the passion to build naturally.
Personally while Mojo Jr. reacts very quickly to stimulus (visual and physical) Senior seems to need a bit more time for passion to build up - and real DFK does it.
It also seems to me that aside from a good snog, nibbling on the neck, ears etc. is also great to give and receive. I love seeing the reaction when a lady gets goose bumps when I start to nibble on her neck and ears - but then that might also be a reaction to the scotch I drink