There are ups and downs to this. It does make sense if you are affiliated with the milonga and you have a real, direct influence on how people dance. It makes a percentage of sense if you can have some sort of a percentage influence. And on the whole, people's behaviour seems to reflect that.
But if most of the people there aren't serious dancers, don't know or care at all who you are, and are horrible to dance with, then there's a lot less point. You can have more influence by dancing with who you want and just setting as good an example as you can, and adding people to the pool from time to time just like everyone else.
In between those two extremes, a lot depends on context. In a smaller community, you can have more influence, and also the obvious downsides that I would imagine - like people expecting you to dance with them all the time just because you did it once, or like people hassling you with demands so you can't dance with people you actually want to and your whole evening consists of wearing yourself out turning down demands and being bitched about, or like people trying out crap to impress you, or like being wrestled around and having the dance you loved turn into a chore - are probably much more controllable. In a place like London I can see why people are risk-averse, and much more risk-averse in some contexts than others. For one thing, in a small community, it's possible to negate these risks by turning other people into better dancers.
I also do think it's quite an important part of tango that nobody has any obligation to dance with anyone unless they actually want to, for some reason or other. What the reason is, is up to them on the day, and nobody else's business. Influencing people is obviously one possible reason, so is community building, so is getting laid. So is having a good dance. But whatever the reason, the dancer is supposed to be self-determining. And that is one of the important attractions of it and one of the important differences from other dances. And this is 100% OK with me, whichever end of it I am on.