Oh they understand the concept. Its just that the recurring revenue and data are more important and without competition or alternatives then why not take everything you can take from the user. What are they going to do? Stop using the internet?
Stop using newer versions of the software. Firefox is open-source, so forking and fixing the older versions before these hostile changes is not impossible.
But also… what people want to do on their devices evolves. Web developers want to be able to support that. So they rely on browser developers to constantly support new features. One can bemoan this state of the world as much as they’d like(*), but at a certain point it’s just sticking one’s head in the sand.
(*) I style myself mostly a native platforms developer, and I’d love it if the web wasn’t the de-facto cross-platform architecture of choice. But alas.