Why is it strange that someone who is single has a single bed? Also live with the 'rents as am not taking out a 120k mortgage to buy a small house and am never renting as that is just stupid. All most as stupid as getting married...
I think I've slept in a double bed since I was about 15.
Gives one plenty of space to play with 'ho's'.

Your stance does rather count on either the property market collapsing or having a big heap of money fall on you from somewhere (this won't work by the way:
http://www.youtube.com/watch?v=ew-h0YLKmrc ).
I was very glad to get out from my 'rents place. The freedom to scratch your nuts in the kitchen without anyone frowning should not be undervalued.
There are other benefits, but I figured this would be one you might understand.

By the way, when your girlfriend breaks up with you and says 'it's not you, it's me' she means 'it's because you live with your parents and have a single bed surrounded by tech'.
HTHs.
Must save on heating in the winter though.