A personal computer or laptop costs around as much as a mobile phone. So I am not sure where exactly you get off on calling me rich. Also, I am not a kid. I think that either you are perhaps the kid who has yet to enter the world of working adults and therefor does not understand that buying a laptop or mobile phone is not such a huge, life-changing deal, even in poor countries. Hell, if you were really desperate, you could buy a very cheap, old used one and it would work just fine.
Playing on a small screen, is uncomfortable. No matter how you look at it.
I would say it all depends on your personal choice that how you want to gamble like for me Mobile phone do the job well but I would say in most of the countries laptop/desktop are expensive compared to mobile phones and all can't afford to buy them so they prefer gambling on their phones only.