Because that's a shitty strategy and just doing what you like and talking to people while there works much better. I'm pretty sure I've gotten more dates sitting by myself reading at cafes and quiet bars that rowdy bars and clubs.
Doesn't work when you like doing functional programming or similar activities ;)
So if your favorite activity is functional programming, do you really think you're going to have a lot in common with people in bars and clubs? Or is the stereotypical person in one of those places really who you're looking for?