Many of the apps that people need to have smartphone to access will not run in an Android sandbox. Banking apps are the obvious example.

Not to mention that the options outside iOS and Android are slim and for the most part bad (or atleast simply even worse than those).

Is it because the sandbox is bad and does not perfectly simulate the computing environment of a real device?

Because to me it sounds like a cat and mouse game that Google and banking apps are destined to lose.