These stations are all part of ARD (actually a "conglomerate" of Rundfunkanstalten der Länder) and ZDF (except Deutschlandfunk, which is a separate entity). So yeah, you already pay for these stations. If you'd watch / listen to them, they'd probably get more attention from the managers and thus the content will be pushed more into the mass channels. Actually, some of the stations are more like incubators for new concepts and shows that they hope to put into the main/mass channels (though others are special interest channels).