Re: Virgin Media
"@AC, VM use their cable infrastructure to provide broadband, they don't need to rent copper from OpenReach, so they have no reason to force you to take a phone service, other than to offset their costs by making a good profit on the line rental."
Your line rental is paying for the maintenance of Virgin's infrastructure. It's not the same thing as phone service. Your connection to Virgin's network costs about £10 a month (averaged, obviously), and then you pay extra for the services you buy which run over it.
Different topology to BT but same commercial principal. See also standing charges for gas, water and electricity which similarly pay for your share of the maintenance of the distribution network.