Basically, copyright. The BBC generally doesn't have the rights to stream programmes outside the UK. Even within the UK, they often don't have the rights to s

Basically, copyright. The BBC generally doesn't have the rights to stream programmes outside the UK. Even within the UK, they often don't have the rights to stream programmes they've acquired for linear broadcast (typically sport). Often they don't have the rights to repeat programmes made by or for the BBC, because they sold those rights to other channels/companies. For example, for Doctor Who's 50th anniversary, they repeated the first story, but could only broadcast it on linear TV, not on demand. Also, the BBC is not the UK government and doesn't fund the NHS :)