Absolutely. A bunch of them also predated the www, or started just when the www was gaining popularity, meaning that information on possible products might be more limited than it is today. Some have narrow use-cases, and some might have started as really narrow in terms of scope, but then ballooned after gaining popularity, sales (and feature requests), and some probably started because the alternative was deemed too expensive compared to just making it in-house.

I think the main point bob1029 was trying to make is that it can be worthwhile doing somehting in-house if the alternatives doesn't match the use-case, are too expensive or whatever else - but that you seriously need to consider if your architecture is the best way to solve the problem before going down that route.