I'm not a fan of Apple's walled garden mindset and resistance to inter-operating with other platforms, but this degree of legacy support is a case of Apple doing a good thing and deserves praise. Note: I'm not saying that Google/MSFT et al are much better than Apple, but they're not quite as bad.

I wonder if this is because some people keep their iPhone 5s around as a backup phone or for some other reason?

My iPhone 5s is still attached to my apple account so a certificate update is probably useful security-wise? But that doesn't seem entirely likely because Apple's account automatically degrades the level of access depending on the age/model/OS version of the device.

I ran a 5S that I bought in December 2013 as my primary phone all the way up to around March 2020, just as the pandemic was really winding up.

The battery, after ailing for a little while, had eventually just given up. I'd gone skiing a couple of times, with the last trip being just before lockdown, and I think it was the cold exposure of the second trip that dealt the mortal blow, and it died shortly after I returned.

I liked that phone a lot. It did, at the time, everything I needed, and it was a really nice size, but that period in 2020 was a bad time to try to get a phone repaired. I did attempt to replace the battery myself using the guide on iFixit but, sadly, that did not go well due to some contradictory/out of order instructions, and all I succeeded in doing was damaging the phone, I think, beyond repair.

Really good to see that Apple are still supporting them though.

I love it when companies keep their old hardware updated.

Instills great confidence.

AMD drops support as soon as it possibly can for "old" GPUs.

tokyobreakfast is right that this is just a certificate fix, not a real software update. But it's still notable.

Lots of old devices become paperweights because of expired certs or backend shutdowns. The fact that Apple even bothered to push this to a 13-year-old device is unusual. Most companies wouldn't.

People complain a lot about planned obsolescence but i'm mildly impressed, even if this update is only to keep the lights on and nothing else.

I remember people complaining that the design of the 5 was already outdated when it was new and they needed to have bigger screens and be thinner to compete with Samsung...

TLDR it replaces an expired certificate, no software is being "updated" here.

Wake me when old versions of OS X can access the App Store again.