i think you're asking just too much there marky boy.
i love shopping in record shops in town
in fact i still haven't bought anything online yet because i'm trying to support the shops for exactly the reason that you seem to dislike.
i like the fact that shops are specialist , you have staff who work there who really know the music and love it ,if you owned a store and you started to brach into areas that your staff didn't know about you would be effectively just trying to play the same game as a chain store , only without the immense buying power to back it up , which is just pointless really.
i'm sure a lot of shop owners would love to be more diverse , but they have to actualy sell records and whats the point of trying to sell hip hop/r+b/ambient/whatever to a techno buying crowd when there's a hip hop store down the road that has twice as much stock and knowledge about it than you do.
no sorry mark specialising is good for business, ignorance is bad for all of us , we need to learn the difference sometimes.