You probably have heard that NDoc's lead developer, Kevin Downs, has announce that the NDoc is Dead. It also came up in the NHibernate devel mailing list, mostly as questions as to the viablity of open source.
I can't tell why other people are working on OSS, some do it for fun, others because it gives them tools or advantages for later on. It is rare that people are getting paid to work on Open Source Software. I know that I started this to sharpen my skills, and right now I am doing this because I like it and because it gives me the chance to do things that I like doing.
I am involved in a number of OSS projects, so I feel that I speak from experiance here. There are no guarantees of the amount of time that an OSS will go if you are not willing to invest time/money in it. If you do, you can either invest your time in fixing bugs, and send the patches to the project, where they are likely to be accepted.
The best way to influence the development of a product is to say what you want, and either help make it happen, or agree to pay for it. Even if your needs will not always fit the mainstream (you want to support NeverHeardOfDB, for instance) release, it can usually be fitted as a native extention to the product.
So, to cut it short, complaining about not getting what you want is not really going to help. You are getting your money's worth.