Sharing piss with your sex partner creates a level of intimacy that normal, 'dry' sex is unable to match, although there should be more drinking of the golden nectar than is shown in this compilation...
This really is a connoisseurs item; love the first scene where the girl on top just starts pissing and carries on as if nothing is happening whilst she snogs her friend; this kind of 'accidental' pissing is fairly rare to see, but excellent.