When software has to "phone home" to deliver the functionality you requested, then two things happen: One, a number of privacy regulations kick in, and they need to get you to agree to send your data to them. Two, they now get to move your data out of your control. I mean, you trust them today, so here's hoping they don't ever get hacked or hire someone untrustworthy?
It's sad when even to use the basic features of a web browser, you need to agree to send them your data. It's not fundamentally necessary to send your data to Mozilla or their partners in order to load and render a website. It's a dark pattern to obtain consent to collect your data "when it's necessary", and then rewrite your app to make it necessary.