Because I don't want my work to be able to literally watch and record every keystroke and mouse-click I make. Much less listen or watch me at home by activating the mic or camera. There's no way I'm using that compromised device at home regularly.
I have a work laptop I only rarely use for just one very specific thing that I can only do on that laptop. I also have my personal laptop where I do everything including my work and if I want to sidebrowse stuff then I open up a different browser—all of which are privacy-hardened.
I just recently got a new laptop so now I have one that is even more locked down, secure, Linux-based, and I only use it for personal stuff.
Depending on where you work, your employer may be able to take that personal device you're using for work in the event of a lawsuit against the company (where they need to retain anything that may be relevant to discovery), or in the event of a security incident (where they may need it for forensics).
I work in information security, and I practice strict isolation for that exact reason. Two laptops, two phones, because if anything ever happens they can and will take devices for analysis or evidence. If you are using an issued device, they'll assign you a new one; if it's a personal device you'll get it back when they're done with it, which could take years.
Edited to add this is dependent on your employment contract, but it's better to be safe than sorry. Cover your camera and use your work computer.
Yeah, like, what the fuck? Why on earth would anyone do that? Do they not own a phone?
Browser history is the most minor part. You should assume that your work sees everything you do to at least some degree. They may have full access to everything on your computer and private browsing won't do anything against that. It's also common that work computers would use a work owned VPN, so they'll at least know what sites you're visiting. HTTPS prevents knowing exactly what you're doing, but a VPN provider will know what IPs you're connecting too and thus will have a high level of what you're doing.
Got that, but still confused. Private tabs in chrome and Firefox do use all the recommendations and history from normal mode in the bar of search or address or whatever we call it now.