I think you could say this about a lot of games. IMO, Apple doesn't make it easy to port a game from PC to iPad (app store guidelines in particular), and I doubt there are as many iPad gamers as there are other platforms.
This is true but Factorio is not Madden; for example they have a sizable (for Factorio) built-in audience of everyone making iOS apps. The pencil would work well for input, I'd gladly buy it again.
