Are you retarded? You think "its just 20c so whats the big deal?"
If free to play game made 200k, and it had a million users, they made 0$, and even if they somehow have a system to 100% accurately recognize each system (which is impossible), after a million installations, they start to owe money to unity, which they dont have. Someone installs a game on a few of his phones, and devs have to pay for each install.