Even in the south east of the UK - compared to the US, an very densely populated area - there are some homes that have wired telephones, but rely on generators for power [1]

Presumably because at some point, it was cheaper to buy 30 years of diesel than to run a power cable, and yet cell coverage wasn't widespread enough to replace a wired telephone.

Of course, we can debate whether providing telephone service is us beneficent city dwellers generously subsidising our backwards rural cousins for the good of their children; or us being taken for fools and subsidising the rich's gigantic holiday homes and rental properties.

[1] https://goo.gl/maps/M1f69iet5mcmKXTr8