Surely it's possible to treat phones the same way as computers in corporate settings? Normal users aren't usually allowed to install whatever they want on their work PC, so why their work phone?
Personal devices shouldn't be used for work purposes to begin with. If work has security requirements regarding what phone and what condition it is in, they better be supplying their own phone to ensure those requirements are satisfied.
No, they don't benefit (cause it means they check work mail on weekends or evenings), but their employer do...