If some crappy website gives me this, then I'm never visiting them again. Good riddance.

Also, it's probably super easy to trick the sites given how you can change your browser's fingerprint (or whatever it's called).

User agent based blocking is stupid, but also, you should really, really keep your browser up to date.

Dev here, there are actual reasons to do this beyond control. It's a small percentage of the overall population of users who require old browsers. Financially not worth the dev time, and most especially maintenance time for fallback behaviors. Over time there are upgrades and new features added to the browser and to the rendering engines that make our lives much easier or add much desired functionality for users. Users on old browsers may not have these and bringing that functionality is either impossible or cost far exceeds that which is pulled in from the the few.

Yep, my father in law got locked out of his bank because of this. He has a Chromebook so he couldn't upgrade anymore, he thought he had to change his computer but fortunately Linux will never be obsolete so I just migrated him to freedom.

It's been like that for years if not decades though.

I think this is not a clean cut case of evil planned obsolescence. There are valid security concerns, as browsers are a common attack vector. You should get that updated, also to protect your privacy while surfing online. So for a banking site or similar, I kind of get it. (I recognize there is a possible conundrum when people can't go bank in person because the bank no longer has branches and/or get excluded by their old hardware/economic reasons from doing it online. Should they be able to choose risking it if the bank knows about a flaw they then leave exposed? Shit's complicated.)

That being said I'm sure this banner of corporate concern was not primarily motivated by the security and privacy of their users.

I built a webapp for work, and when a new PR firm / subcontractor entered the picture, they complained that it didn't work. I spent hours pulling my hair out until I figured out that they were using a seven year old version of Safari. Apparently, their laptops stopped receiving system updates from apple, and you can't upgrade safari alone. As someone who has never used an Apple computer, this blew my mind.

I have an old iPad Mini that is long outside the support deadline for Apple. It’s using AltStore instead now, but when I tried to install a patched version of Spotify, the app and even the web app, completely blocked both the OS version and the WebKit version. I can’t even use the web version of Apple Music on it. The amount of artificial locks these companies use is annoying as fuck.

It's mostly age verification services. Some Lithuanian service blocked me this way when I tried to sign up for a Wise account.

Older browsers don't support features that the pages are coded with. This could be security or just layout issues. It's difficult to support older browsers, or just the volume of browsers x versions. So it's reasonable to limit the test space. And it's usually easy for users to upgrade.

Probably part of the plan to to take all the hardware for data centers, make it more expensive to buy, and force everyone to rent services from their servers rather than own a computer.