You say "doesn't happen quite often", which I'm assuming means something like "doesn't happen quite often to me". But if you consider hundreds of millions of u

You say "doesn't happen quite often", which I'm assuming means something like "doesn't happen quite often to me". But if you consider hundreds of millions of users using Firefox every day, then even a relatively rare event is happening to multiple users every single day. It is absolutely worth it to them that Firefox does its best to preserve their data.