Because usually the developments are agreed with the developer having to build these services as well as part of the agreement, or having a s106 agreement. There's a few in Coventry where locals have been told they'll get schools, doctors, community centres etc. that have never materialised. I think more rural developments get a bit more than developments in cities etc. but the developers will obviously get away with as little as possible. With the s106 where money has been given, it rarely gets spent on the services because so many councils have no money because govt fucked them over with the social care bill.
Trouble is they let them build the houses then *shock* they say they've not got enough money left to build the services or they'll lose money, and they just get let off.
How about telling them they have to build the services first, and cannot build more than 25% of the housing until the services are in place? With the services built and in place the houses they build after are more valuable to them.