Less than 70% of the TV licence is used to fund BBC TV. Even if you could get away with not buying your TV licence, by not watching BBC TV, you'd presumably have to also do without all the other services which the TV licence funds.
You wouldn't be able to listen to Radio 1, 1Xtra, Radio 2, Radio 3, Radio 4, Radio 5 Live, 5 Live Sports Extra, 6 Music, BBC7, Radio Scotland, Radio Wales, Radio Ulster, BBC London, 41 other local radio stations and the BBC Asian Network.
You also wouldn't be able to access the world's largest website, BBC.co.uk.
Although you might be happy to do without BBC1, BBC2, BBC 3, BBC4, BBC News 24, BBC Parliament and BBCi, your children (or any kids who visit your house) might be less happy about missing out on CBBC and CBeebies.
The BBC also owns 25% of Freeview. Without the solid financial backing provided by the TV licence, Freeview might never have got off the ground.
If large numbers of people didn't pay the TV licence (by claiming that they never accessed any of the services which it provides), the licence would have to be abolished and the the BBC would be funded by advertising. ITV strongly oppose such a move because there's not enough advertising revenue to go round. (It's likely that many ITV services, particulary ITV1 which costs a great deal to run, would have to close). Similarly many services on the Sky platform would also go out of business because of a lack of advertising revenue. So the TV licence effectively subsidises commercial broadcasters by freeing up the advertising revenue which they need to run their services.
Chris