Why ? we already have plenty of cities and towns.
Problem is that it's really just Orgrimmar, Stormwind, Dalaran, Shat and the shrine that has all or most of the utilities, so they are the only ones that are really used.
i'd rather have them make existing cities and towns more use-able, instead of just adding more that won't be used outside of questing.
The way I have imagined myself in WoW since I started playing was that everything we see or do is actually just a different Scale of the World.
I.E. Stormwind is Massive in Lore but the city we see is just a scaled representation.
When we mount up and run across a field between 2 quest areas we are actually riding quite a far way and the Town hubs are just a small scaled representation of what is actually there.
Well in the case of Guild Wars 2 you have 3-4 good cities, Divinity's Reach, Black Citadel, Lion's Arch and Rata Sum, and then you have Hoelbrak which is okay and the Grove which is really disappointing. But, it's really a different design philosophy, Guild Wars 2 places a great deal of weight in environment design and every zone is designed to the dreams of the artists involved then scaled back in order to make it actually playable. WoW on the other hand places a much lower priority on zone design and reuses assets as often as possible. I don't think that bigger cities would help much because at a point they'd still be using the exact same building lay-outs, just with more of them.