I feel I ought to participate in this thread because it's about an issue so close to my heart, but most points have pretty much been made, and we all largely seem to be agreeing.
I don't think it matters that there are lots of micro-breweries producing much the same sort of product. It's inevitable that many ales will be very similar to each other, perhaps with only very subtle differences. But if the product's good then that's the most important thing, and if it's not (i.e. producing bland ale), as others have said, they will soon get found out.
And again, as others have said, it's up to the landlord, or his/her hierarchy, to give the customers the choice they want. But it's horses for courses. There are many pubs I know where with the best will in the world all their customer base will allow them to sell is just enough ale for them to have one on handpump. In that case, in this part of the world anyway, they generally go for London Pride, because it's seen as a tried and trusted ale, and you really can't blame them for that. But where a pub has the custom to sustain half a dozen ales then they really should give customers decent choice. I've been in my local 'Spoons where they've had five or six ales on and all have been stouts and porters. Nothing wrong with stouts and porters, it's just that I don't care for them and that's my choice. Another pub I went in had six light hoppy summer ales on. All I'm saying is that where an establishment has the ability and wherewithall to offer a choice, they really should make the effort to do so.