The bookstore analogy is nice, but I'd refine it like that:
A bookstore specialised in romance, or even in a specific type of romance, would make sense in a big city with many, many bookstores.
However, if it's the only one, or one of the few, of a small city, this would be terribly frustrating.
It would still possibly make sense, if it's what sells the most (eg. If the bookstore started as a generalist one, and then specialized on romance because that's the biggest sale %).
However, it's very dangerous long term on a business point of view, and it's frustrating for the local community.
On the internet, it's different because there are plenty of 'bookstores', but most have no or little visibility.
So, we can go to the nice romance bookstores on the highstreet, or we can search, with uncertain results, for different things in the back alleys.