So do you have a work phone number?

I don't have work number currently. And I very rarely call with my phone to coworkers.

when you could just organize your work applications in a single area

You could do that, but you would miss some of the features. Ex. I use same browser on normal and work profile, but I have two icons (one for work, one for normal) to open browser. When I'm on my work profile, I'm logged in with my work Google account and it doesn't interfere with my normal profile browser. Same thing for Gmail, calendar, contacts, Google docs/sheets etc. And if I ever want to get rid of works stuff on my phone, I just delete work profile.

And for security reason when normal profile apps cannot interfere with work profile apps in any way. Ex. I can have one password manager on my work profile and another on normal profile and they cannot share information in any way and I can keep my work and private passwords separate.

And like I previously said, this works for entertainment use also, as I can have two instances of same app with different login information (like pokemon go)