Chugalug,
To put it very simply, because it is the last place, in the UK, that has any semblance of freedom of the press.
Furthermore, they make shows that need to be made but would not make it past the money men and advertisers on the commercial stations.
Before you respond please remember that this is purely a matter of opinion on all sides since there is no empirical measure that any of us can use for the sake of comparison.
Cheers
BHR