Not that this entirely clears the skepticism, but to directly address the question as asked: blocking ads scratches a clear itch for the author. FOSS works great because software has no marginal cost, so as long as someone wants it to exist badly enough to make it so, there's then no reason not to give it away to anyone else who wants it. Providing a free VPN service to the world is quite a bit less likely to be an author-itch, and actually incurs a cost.