How do you know this? Of course there are lots of reasons for why they'd want to enforce minimum browser versions. But security might very well be one of them. Especially if you're a bank you probably feel bad about sending session tokens to a browser that potentially has known security vulnerabilities.
And sure, the user agent isn't a sure way to tell whether a browser is outdated, but in 95% of cases it's good enough, and people that know enough to understand the block shouldn't apply to them can bypass it easily anyway.
simply reading the browser agent isnt really security
It's not for their security, but for that of genuinely clueless people that are just running an actually outdated browser that might have known and exploitable security flaws.
Some fake Telekom workers showed up at my grandma's place in person recently, wearing uniforms and all, saying they need to "perform maintenance on the TV connection". Luckily, grandma's still super sharp, recognized that something was off, and just shouted "Peter, the TV people are here" into her flat, even though she was alone and Peter had died decades ago. They made some excuses and left immediately when they thought they were no longer just prying on a single brittle old lady.
Super proud of her, but also so scary to think that a bunch of asshole scammers were so close to just walking around in her flat.
Oh Mann, wie leitend diese Antworten formuliert sind. "Nein, ich will mit meinem Auto weit fahren und auch ankommen." Als ob das mit einem E-Auto nicht möglich wäre, geschweige denn in 2035.
Und dabei hat die CDU doch extra nett gefragt, dass jeder bitte nur einmal abstimmt. Hätte echt niemand mit rechnen können, dass sich da keiner dran hält.
Alle "linken" und alle "rechten" Parteien sollten sich einfach jeweils zusammenschließen. Dann kann keiner der Parteien die ja sowieso genau das gleiche wollen sich gegenseitig Stimmen klauen, und für den Wähler ist es auch einfacher. Entweder oder, wie ein Fußballspiel. Funktioniert doch in den USA auch wunderbar.