4. They network elsewhere
Many views on why they do, and why it's so fragmented. But fragmented it is.
5. London is flat and wide with the startups not centralised
Not everyone is around Old St, and even those who are might still be grinding out code when the meetup started and then just opt not to walk in halfway through. For the ones further out, timings and stuff might put them off. People don't live around their either so it may be a trek home for some that puts them off.
6. Topics might not appeal to them
Then there's those who might go for the topics, but weren't interested in that set of topics.
7. They don't wish to have the distraction of networking when they just want to keep their heads down and get on with it
And those who have what they feel is the network they need, and so invest their time in that network alone.
I didn't go, even though I have intended to go to the last couple. The reasons above aren't my reason, but I'm speculating that there are more than just the reasons you give.
And I do have a startup (a small but profitable one, it ticks over nicely and I have a few things in the pipeline to help push it a bit further). And across the office I see another guy with a startup who managed to sell recently. And then there's people I know down near Shoreditch working on stuff. The people are clearly around, but none of the ones I know went last night.
Just asked a couple of guys here. Reasons given: Formality and agenda, hanger-ons, recruiters, aimless networking.
Concensus here was that if it was more to let off steam and pressure with a bunch of like-minded people sharing the problems informally over beer and fussball (yeah, we're thinking Bar Kick)... then most of them would be good for it.
Also, there was the shared view that DrinkTank was pretty damn good whilst it was very small, invite only and vetted (people actually doing stuff).