Big monitor or two is needed more than absolute top line cpu performance - I use a small nuc like system at work as a desktop.

At home, I have a PC with a big monitor for gaming and I ssh to my macbook for dev work from that using the ubuntu shell.

Certainly screen real estate is important, but somewhat irrelevant to my question. I already have the monitor situation covered, so it's not like I'm having to make a trade-off between pixels and performance.

Just to clarify: I'm not asking whether a workstation desktop is necessary. I understand that it's not. I'm asking to whether it is a good investment, and how people have made that work with their employer's IT policies.

I don't know about IT policies, but I think any reasonably good IT org would just consider everyone's machine compromised -- owned by employer or employee both and take security measures commiserate to the needs of the business.

Regarding it being an investment - if you think anything can make you more productive and you can get the business to pay for it - sure, why not? Could be a chair or a desk or a coffee maker or a computer.