"TV licensing" exists in a lot of countries and it funds the public service broadcaster. It is essentially a tax, it just happens to be collected by a third party (in this case, Crapita) rather than other tax collecting mechanisms.
Some countries (like Finland or Switzerland) require you to pay it even if you don't own a TV. It's really just a tax.
The reasoning for it not being a tax is that the public service broadcaster should have political independence from the government. Most people don't want their country to have a "government mouthpiece" state broadcaster, and it is much easier for the government to tell the broadcaster what to do and say by fucking with its funding if it's directly funded from the treasury.
Other countries do the same thing with a different trick, such as inserting it into your electricity bill.
The UK is a powerhouse in media production, part of that is due to the BBC funding all sorts of productions, both the visible (actors, etc.) and the invisble (camera operators, set designers, costumers, writers, directors...).
It has also been clear for centuries that private media, historically just the newspapers, but now TV channels, film studios, etc., have been disastrous, as their private owners either focus on profitability and pump out scandal and lurid stories, or if they've made their millions some other way, they run a paper in order to pump out biased propaganda. So a state-funded but not state-controlled broadcaster is an ideal thing to have.