Aren't most fonts licensed in the apps you use to make things and the OS it runs on?
No - the licences often don't cover broadcast and other commercial use. You often need to specifically buy a licence that includes broadcast rights, and they aren't always that cheap.
The BBC already have an 'in house' font in widespread use. It's called 'BBC One' and is the typeface used for the BBC 'one' logo and on-screen elements used for BBC One's presentation. (It's also used widely by The One Show as they use the BBC One channel identity in their on-screen look)
Mike W and elmarko gave kudos