The "hackability" (and decrease thereof) isn't something exclusive to games - just look at what happened to the UIs of popular programs like browers, for example. Everything is becoming hidden away and more difficult to configure.

In contrast to the many menus and dialogs we had before that encouraged users to explore and customise, it seems that apps now are far more opaque to the point that many users don't even realise some things are options that can be changed.

That ecosystem isn't just unavailable in mobile games, but would probably be hated by many companies who want full control over their product

Perhaps it's a bit of a stretch, but I think the whole "war on general-purpose computing" has played some part in this too.