I don't get it either. But I guess they are are concerned about Mr. Disgusted, Cheltenham complaining: "I don't see why I have to pay my license fee AND suffer these interminable commercials".

Come to think of it, it may be in the BBC's Charter that their content be free from commercials (to license payers). If so, they are contractually bound to hide the commercials or, keeping it simple, just not provide content with commercials to license-payers.

Of course, most of the BBC's internet accessible content has always been geo-restricted in the opposite direction. So they have form there.

BBC.com shows ads to people geolocated outside the UK. Most of that content is not blocked to the UK.

Here we see something a bit different - the article is blocked to people in the UK.

http://www.bbc.co.uk/bbc.com/faq/

Because BBC Worldwide is a commercial organisation and the BBC (the parent company) is a public service broadcaster. Even though BBC Worldwide is a subsidiary, if it started publishing content in the UK (where it has no commercial interest), it would give rise to a conflict of interest. You could argue that if BBC Worldwide were available in the UK without advertising, then it would in effect mean that the parent company was licensing content from a commercial partner.

Murdoch complaining about unfair competition