It cuts both ways.
I live in the UK. Here the obligation is symmetric. All my recent work has been on 90 day terms. That is, if either I or the employer wish the contract to end normally that requires 90 days of notice unless both parties agree otherwise.
My most recent employer decided their costs were too high compared to projected income, so they gave me 90 days notice back in 2019.
At that point I knew that in 90 days I won't have a job. I could start looking for a new job, able to tell any prospective employer that I can start on day D+90. I would still get paid, as usual, and my employer was entitled to insist that I continue to work as usual.
In fact of course they gave me garden leave, I guess that's probably an alien term in the US too? Garden leave means that the 90 day term still applies, you still work for them not anybody else, and they still pay you fully - but your employer thinks it would be best (for example because they're scared you will sabotage things, poach customers, or steal trade secrets) that you do not come to the office or use their computers and thus you cannot do your job.
I'm very awkward so I pointed out that they're short of cash, rather than having too many engineers, and so since I wasn't doing anything else I kept working, although I will admit I wasn't exactly the most motivated team member since I knew I was terminated. They had to go re-enable my git access, AWS access and so on, which had been severed when I went in to be told I was fired. Very amusing.
Now, let's roll back to my previous job. I'd been essentially head-hunted, I informed that employer that I'd be leaving, triggering the 90 day notice. I was actually at their offices at the time, (I usually work from home) and I informed them that I'd be available until close-of-play to negotiate the exact details. They got right down to the wire but eventually sent someone to work it out, and we agreed I would spend the notice period spinning up people who'd been brought in to learn what I do, and that I wouldn't take my vacation days, but I would actually leave on D+85 not D+90.