Because in most cases you don't want different applications to use different settings.
If you are currently using private DNS server with internal domains and don't know about changes firefox is going to make, firefox will resolve you domains incorectly
while all your tools like nslookup and dig will show correct information.
And then when you do figure it out, you will have to go to every single user and help them fix firefox setup. (because most of such small businesses don't have their own AD)
I first though about blocking it at companies firewall level, but thats tricky, because you don't want to break everything else that uses cloudflare.
If you are currently using private DNS server with internal domains and don't know about changes firefox is going to make, firefox will resolve you domains incorectly while all your tools like nslookup and dig will show correct information.
And then when you do figure it out, you will have to go to every single user and help them fix firefox setup. (because most of such small businesses don't have their own AD)
I first though about blocking it at companies firewall level, but thats tricky, because you don't want to break everything else that uses cloudflare.