Because mobile work is just the reality now, especially since more and people are working from home full time. For me personally, as a busy parent who works from home for a large corporation, I need to be able to take care of things during the day if the situation comes up and I happen to be in the waiting room at an orthodontist appointment for one of the kids, in line at the pharmacy, etc. I am limited on my personal devices to what I can access through Office 365 through Duo 2FA, so there are no profiles or security measures from my company installed anywhere--they are completely out of my business other than what's on their MS instance.
In order to be sure I prioritize my personal life, I have focuses set up so that after a certain time, I'm not going to see work emails or messages, and I have notification badges turned off for those apps so they're never bugging me when the Personal focus is on. Because iOS now has this capability, I am much more willing to at least have the key work apps I need on my iPhone/iPad in order to take care of things on the fly.
In my eyes, this is a win/win/win. I have very nice work-issued MacBook Pro that is my main work machine. I have my mobile devices that can fill in when needed but don't have any prying eyes installed. I have my own MacBook Pro that can't access any of it and is completely walled off.