I had a really bad meeting one day that became the straw that broke the camel's back. When I went back to my desk, I saw an interesting job posting. I immediately fired up the company's copy of Word to draft up a resume, and used the company computer to send the email from my personal account. Less than a month later, I was working for the new company. It was done intentionally. I almost sent the resume via company email, but I really wanted to ensure I could access any response.

> It would never occur to me to use an employer's hardware for such a purpose

That's a very uncommon mindset and worldview.

For 99% of people, the default would be "I'm going to join this Zoom meeting from the laptop I use all day long to join Zoom meetings, and I'm going to code using the laptop I use all day long to code".

Lots of people have their work tools setup on their work computer, but not on their personal computer. Their personal laptop might be relatively underpowered and struggle to run all the required software efficiently during an interview. The issue becomes even more significant as more of the tools used require an account - you don't want your interview performance to suffer because you're using an unfamiliar tool or service, so you just use the ones you're used to using every day.

If you work from the office, and they have tight security, they might frown upon bringing personal devices to connect to the internal network.

Also, some people might not have dev environments set up on their personal devices. Heck, a lot of people only use the internet through their smartphone, when they're not at work.

For my most recent job (Staff/Principal SWE) I interviewed at four companies, each with four rounds of interviews (usual variations on 30m recruiter screen, 45m-60m tech discussion or coding exercise, 60m-90m tech deep dive, 30m-45m final wrap up with hiring manager). All over the course of about 3 weeks. It was about 16 hours in total.

No chance you can do that on "sick days", fake doctor/dentist appointments, or other such scheming. Taking many half days of personal leave just isn't workable either. You're not in full control of the scheduling to make different companies interview you one after each other on the same day, or take the same time between rounds. Some could have been scheduled in lunch breaks but not all of it.

Most people I've worked with would just schedule some "focus time" and were either WFH or headed off to a quiet part of the office or a nearby co-working space. Personal laptops are easier to use offsite obviously.