Re: the Beeb don't do anything that is or requires a natural monopoly
Agreed. However, the BBC is required by law to be impartial. Commercial stations just have to make a profit and keep their owners happy. That's a pretty big difference and one that I think is worth paying for.
Sky News do a great job and arguably outpaced the Beeb some time ago. MP's expenses, the biggest political scandal of my generation, was broken by The Telegraph. Meanwhile the Beeb quash Jimmy Savile stories while bothering the airspace over Cliff Richard's house and there are certainly many individuals within the BBC who are anything but impartial.
It's not as good as some people think it is, it's certainly not good value (it's just that lots of people pay which get the individual price down) and while it exists it stops something good coming along to replace it.