Browsers shouldn't require accounts, and thankfully Firefox doesn't. But having a way to synchronize my passwords across all my devices is pretty important.
*) Or whatever the real reason was. It was about time Mozilla started to have management issues so I absolutely won't be surprised if the goal was to "become an ecosystem" or "gather a userbase" (or whatever is management speak for forcing people to sign up).
How is that not still an account? What definition of account are we working with here?
You used to just open two Firefoxes, start sync setup on the one, copy (or scan) a code to another - boom, done, they're talking to each other.