Or you fancy some random banter.
You prefer good conversation and the odd debate rather than a drunking night of noisy pubs and a hangover.
Or your a geek and want to game together and brag about the number of pixels your gfx card can push.
You play warcraft or are L337
You hate football, neds,junkies and scroungers.
You secretly laugh at sick jokes.
And you really must if you laughed when filling out the children section, and had to leave it blank as there no "no kids" answer, only "likes kids". You get the jail for that nowadays.