This is certainly a very good reason to not put your work account on your personal phone, but my primary reason not to is that it's my device and I pay for the service. If my company needs me to be available beyond my 9-5 workday, they can pay for it. If there's an emergency, they can always call, but I don't like being "always on".
I recently got a new job where the email is completely locked down (only accessible on a networked computer or via the awful outlook web interface). It's been awesome not getting work emails on my phone.
When I got a new phone, I simply didn't install the email or slack clients. It's led to occasional text messages, when I really needed to communicate with a team member, but all in all has been a fantastic experience. Highly recommended.