There's been some complaining on doctorwho about people writing stories where the Doctor and Rose make with the making babies thing. They didn't like the idea of the Doctor having sex. I'd like to say that they should blame the show writers.
Let's say for a moment that I wanted to write some porn involving Rose and [insert male character here]. I could go for a femal character, but for the sake of this argument let's say I wanted to have a story with straight sex in it? What choices do I have for a male character?
Rose: the Doctor, Mickey, Auton Mickey, Clive
End of the World: the Doctor, The Moxx of Balhoon, The caretaker bloke
The Unquiet Dead: the Doctor, Charles Dickens, the bloke wot kidnaps Rose
The Aliens of London: the Doctor, Mickey
Not really much of a selection there. The only other character even worthy of consideration, IMHO, is Mickey, and frankly the way the character's written makes him come across as a bit of a twat. AutonMickey might be good for some laughs.
So blame the writers for not coming up with any other suitable male candidates.