I agree with Taitu on this one.
People seem to be worrying about the plug-in being all-inclusive, like they deserve free online lobbies for their games.
You want to set up an MMO or an online lobby? That is YOUR responsibility to get it set up. Scirra should not be in no way required to supply a public server in this regard.
I feel like we have missed half the picture in this thread somehow. For years people have been getting along fine with simple P2P and LAN functionality. A lobby makes P2P easier, sure, but a lobby for YOUR game is YOUR responsibility to set up.
And just in regards to the question of "how many people will use" the plugin without a supplied server. I, and quite a few other people here I am sure, primarily play games for the multiplayer experience. A few years ago this may not have been true, but gaming and multiplayer really do go hand-in-hand in this day and age.
Hell, If I understood C++ to any reasonable degree, I would be making a Raknet plugin right now. All of my W.I.P games depend on it.