The government care and does not want you, underage future voters, to learn dirty adult things too quickly and ruin your innocence. Never mind that the 'forbidden fruit' phenomenon is well recognised by psychologists, that there's far worse things readily available online than scenes of sexual nature and that it's parents' duty to put boundaries on children' access to digital media.
The government needs you to stay focused and clear minded, not busy slobbering over unrealistic displays of disgusting digital trickery. Never mind that censorship is universally considered a breach of freedom of speech, restrictions will expand until they suffocate all but the pre-approved content and such government controlled media can only end in happy, happy, we're all so happy propaganda.
Ironically, I just tried to access a BBC page with an article about porn censorship and was greeted with: We're sorry but this site is not accessible from the UK.
It has began!