I'm pretty sure it's just exposure and time. Mobile is a great format for keeping yourself entertained on a subway. Desktop or console is a great format for actual games. People have more phones now because you need phones and you don't need desktops - that has nothing to do with the enjoyment you have gaming on each.

You used to be able to dial TIM on a landline phone to check the time (for free?). Then you (if you were a computer nerd) checked it on your computer, then on your cellphone. Because that's what was available. There was no connection between knowing the time and landline phones - people just had landline phones so it was a convenient way to deliver the service. That's how it is with mobile games now.

Remember Java and Flash applets? You could make anything you wanted as a native application, but RuneScape took off because you didn't have to install it.

I've got college-age extended family members who don't have any memory of a desktop PC like thing being in their home. Parents might have brought home a work laptop from time to time, but outside of that by the time they were like five the family machine had already been scrapped.

The "big family computer" became an iPad.

The Steam Deck is basically a way to play PC games on mobile. You can imagine a world where people can just plug their smartphone into a KVM and just use it as a gaming PC. Modern phones have enough computing power to play most games being produced today since a lot of them are indie or B titles that aren’t actually that intensive. And even the intensive AAA ones, if developers were willing to optimize for it and go for lower res graphics they could do those too. And they can definitely play any game that’s more than 10 years old.