[Renaud]

You seem to forget that the US is about 5x the population of the UK. Voluntary donations are nice but assuming generosity in the US and UK being the same, the UK would end up with 5x less funds than what PBS and NPR have (about US$550 and $270 yearly, respectively).

The BBC has about US$6.5B and produces a much wider array of programmes than PBS and NPR combined. So not relying on public's mandatory contribution would clearly not work.