I also just want to say, as a full time remote worker, I need Slack on my personal phone. Remote work allows you to work anytime and thus break out of the 9-5. But to properly do that and still be a member of a team, I need to be reachable on my regular phone. If I decide to switch up my day and work at night, I need to still be reachable for random things during other people's working hours. It's usually just someone has a quick question. Team members in other time zones have discussions on Slack that are outside of the time I'm sitting in front of my computer. I like seeing these discussions and contributing while I'm at the grocery store or some such. If mission critical software is blowing up, I need to know that I need to get back to my computer. If I don't have any real work to do that day, I can go do something else, and just check my phone to see if I need to get back to my computer because someone who actually is working needs me. I can actually sort of take days off this way, without having to actually ask for the day off.

In general, as a remote worker, having Slack on my personal phone allows me to work less and more efficiently. It gives the illusion that I am always working, whereas I'm actually working only when I want to and am most effective.