As much as the private sector is supposed to be able to move fast and adjust, that’s just not the case. Change isn’t easy. Sometimes, a position just exists because it always has. Certain processes have certain roles in them, and nobody wants to take the time to scrutinize whether those roles are still needed.
A lot of white-collar work is related to risk aversion and having several eyes on decisions or processes, so there is some kind of built-in excess capacity by design. It’s a margin of safety, even though said margin can be excessive. Whether or not leaders know that, adjusting can be harder than leaving things as is.
Managers may well realize they’re not using their staff well, but whether they do or they don’t, it just gets really hard to change those processes without somebody making that their priority,. If it doesn’t feel like it’s broken, then no one’s going to make noise about fixing it.
Being in the office does not guarantee you’re working, either. People slacking off on the job long predates remote work
To put it plainly, the stock market is not representative of the whole economy, much less American society.