Note that there are loads of things that you can't keep working on after you retire. If your company had you in a position where you ran really interesting projects, all of those are the company's projects, not yours. You got to work on them because you worked there, and once you retire you can't just keep working on them, you can't even do the same work on your own because your contract made that pretty clear: now you're committing IP theft.
So you retire, and by law you're no longer allowed to do the thing you love. It's not a good deal.
You can be "retired" (don't _need_ to work) and still have a dayjob. My father-in-law does this and works 2 days a week so he doesn't get bored and has a little more spending money, all because he likes his profession but not because he has to work for a living anymore
It's pretty cool that you have such detailed knowledge into everyone's personal circumstances that you know they all have employment contracts and what the details of those contracts are.
Most people reading this right now are in the US, and the vast majority of US employees at at-will, which means no contract at all. Even for those with contracts, it's a pretty big leap to get to "IP theft" with anything anyone could reasonably work on in retirement.
What made you read that comment and go "they're talking about everyone" instead of "oh, yeah, those people also exist, blanket statements don't make sense in this context"?
The things I love are broader than "IP controlled by my company." I can see that if the thing you love is massive financial institutions or defense contracting or something?
Or, you know, you're a specialist who worked their way into a career at anything that produces hardware. Philips, Samsung, heaven forbid you work for a larger corporation, how many of those people can there possibly be, right?
You have won. Yes, if the thing you love specifically requires the collection of capital then of course, you will have difficulty finding that outside a corporation.
I suspect with analysis this is not the case for the majority of folks.
Hardware is a funny example though, because I feel it's easier than ever to get some interesting hardware stuff going.
So you retire, and by law you're no longer allowed to do the thing you love. It's not a good deal.