Still, I think "aw, shucks, little us?" thing is kind of silly. Without that fame, would they still be raking in so much money?
They've explained this on multiple occasions when people ask them how to repeat their success without their advantage of having a big audience and (relative) fame: they didn't have that when they launched Basecamp.
They had a blog, but not a huge audience like they do now — they certainly did not have a bigger audience than is possible to build up through "traditional" blogging means (writing great content that people like to read and link to).
37signals is an excellent case study of a company which has built a profitable successful business without any kind of fame or following. Because they weren't famous and they didn't have a big following and Rails didn't exist, way back in february of 2004 when they launched Basecamp.
However, small, simple, and few features makes for a very low barrier to entry if that's all they have, so I'm not sure it is a very good model unless you are famous like they are (that's their "barrier to entry"). In other words, they are something of a special case, not really an example to be followed, even if what they've done is admirable.