Want code to be open forever, and for you and your contributors to not be taken commercial advantage of? GPL could be a good choice. Do you desire total world domination (for a new protocol, for instance) then go with something like MIT that allows both open and commercial implementations to interoperate easily, without a lot of license drama.
And yes, some people may "feel" as you say, that they only want to contribute to GPL projects. Sometimes for religious reasons, sometimes other reasons.
For my part, there are some kinds projects that I would not contribute to under MIT/BSD style license, because I would want my work to be available to some community without being taken advantage of. Certain pet hobbies of mine fall in that category. OTOH, there are many BSD license projects where I am happy to send a patch or two because I benefit from the ecosystem in numerous ways, including commercial support for said BSD software.