For what it's worth, I'm near 40 and have never once seen anybody at any work place wear a suit (who wasn't giving a speech at a town hall).
There is nothing wrong with wearing a suit, and it may be common in some workplaces/cultures, but in others it can be corollary to a work culture you are not compatible with.
In 2024, at a tech company, I wouldn't find it common. But, especially for people who may have customer-facing roles, I probably also wouldn't find it worthy of comment or really a second thought if someone in the office was wearing one.
When I last interviewed 15 years or so ago, I wore a jacket and tie (though not a suit) when I interviewed in person. I certainly didn't think it was necessary but I'd have been shocked if anyone had considered it to be a ding.
My guess is it just doesn't fit their style. Some people want more formal clothes in the workplace and others would rather not have a dress code. Even then, just the interviewer wearing a suit doesn't necessarily mean it's a strict dress code culture, but probably a strong signal.
There is nothing wrong with wearing a suit, and it may be common in some workplaces/cultures, but in others it can be corollary to a work culture you are not compatible with.