I think the stigma with pirating a premium PC game is higher than "just" pirating an Android game. I know a lot of people who see mobile apps as disposable and so have no problem downloading them for free. A PC game like Doom carries a different weight to it that makes these same people at least consider the premium purchase. Not saying it makes any sense, but that's been my observation.
It's certainly more difficult to pirate a PC game than an android game. Maybe the difficulty of figuring out how to run cracks and the fear of accidentally downloading a virus is the X factor. The whole process is much easier, less riskier and overall feels "nicer" than pirating a PC game or app, that's for sure.
While that's true, that's no different from PC games and they still make considerably more than android games do. There's definitely an X factor here.