Yeah the changes in government is a big thing I think. In the US nobody can be president for more than 8 years (in theory at least, I guess you guys will be testing that in 2028) and in place like the UK no Prime Minister really lasts more than about 10 years at most, and that's pretty rare. Nobody wants to do all the work and spending on something that will pay off for the next person, so it's sort of hard-coded into these systems that any project which takes more than a decade to finish probably won't get done.