That would be a firing offense at my company. Company files stay on company hardware. Personal files stay on personal hardware, and never should the two meet.
Not the OP, but personal files are not just vacation pictures. I work in R&D and I have my org-mode/roam on various scientific and technical topics going back 15 years or so. I use these for work to benefit my current company, and maintaining two parallel versions of these is rather inconvenient.
Isn’t that exactly what a cloud drive is for? There’s a difference between using your personal notes for business purposes on the one hand, and keeping company property and data on a machine totally outside IT control. That’s just a massive lawsuit waiting to happen, and it’s bad for the employee too - why would you want the liability?
I would't store company data or code outside of approval services, but one might say that my notes, including notes on the people I meet and projects I work on, can constitute proprietary information - so yeah, it is a bit of a grey area still.
That may be sensible if you want or need stronger security and isolation.
However, many companies do support BYOD, especially on mobile where it's a pain to carry two phones around.
There is some support for this. For example, Apple supports dual Apple IDs and separate encrypted volumes for personal and corporate data. Microsoft apps (Outlook) also have some support for separating personal and corporate data.
The benefits of BYOD can include lower equipment costs, lower friction, and potentially higher employee happiness and productivity.