I believe Valve dropped official Windows 7 support in Steam because Chromium did and they weren't going to fork it.

I empathize if you don't like any version of Windows newer than 7 or XP, but it's time to let the dream of running them forever go. It's not weird when software doesn't support the 2009 version of an operating system anymore in 2024. If they never dropped support, it would be difficult to take advantage of improvements that occurred in the last 10 years, because we'd forever be stuck in baggage.

Of course when it's feasible everybody loves software that really never does drop support, like 7-zip, which I think happily still works on Win9x without KernelEx... but I'd rather 7-zip stopped having serious security issues than continued to work on old Windows versions.

Windows 7 was great and I'd love to go back. If I really had my druthers, Windows 2000 was peak and XP was just a vulgarized version of 2000.

However, it is Microsoft more than anyone else that has decided to stop supporting those operating systems. Windows XP does not have support for any modern version of TLS (only TLS 1.0). There's no good way to support a browser-based app like Steam on a platform that cannot natively provide a secure connection to a modern web server.

There is not such a hard reason to drop Windows 7 support (again, except that Microsoft no longer supports it) but there are security-relevant APIs that are only available starting in Windows 10 which means special patches would have to be maintained just for Steam on Windows 7 to continue working securely.