They did. Support was discontinued from the start of 2024. That you've been using it up to now without any problems is literally because they didn't break anything on purpose. As long as none of the software changes it will continue to work.
https://help.steampowered.com/en/faqs/view/4784-4F2B-1321-800A
That's generally not online platforms, though. For obvious reasons, those have ongoing operating costs