I don't think any mid-large company allows 2 anymore. Access to company resources always comes with an MDM policy.
In other modes (COBO, COPE) it's not but those are much more difficult to enrol, as you have to do it from the setup wizard on a new phone or after a factory reset. So you don't happen to get into this mode by accident. They're only used for company owned phones (this is what the CO part stands for).
Of course most companies provide phones, but many users prefer to use their own, both for the benefit of having to carry only one, and because they have more choice.
Another big benefit of work profile is that you can switch all work stuff and notifications off with one click! I really like it overall, it gives great separation.