Agreed, although I don't know about niche (a lot of people knit...) or underserved. There are numerous resources and communities for knitters and crocheters out there. The only reason why I love Ravelry over them all is because it manages to wrap everything up into a nice user-friendly website that (if one cared for them) is packed full of all sorts of useful features that other sites couldn't even begin to offer. Try to find another knitting community online where you can look at a pattern done in another yarn without attempting to knit it (and possibly wasting a lot of time). It's a lot harder than you think. On Ravelry it's a single click away.

Ravelry doesn't even replace half of these resources out there - most of the patterns are still going to be in books and magazines or on other websites, all the knitter bloggers will keep on blogging on their own sites, people will still go on other forums for, say, a specific yarn brand to ask questions there. But it is the glue that holds it all together in a single place so you don't have to go searching in Google and half a dozen sites to find patterns and talk to other fiber arts enthusiasts.