Why do maps apps have essentially no caching?

I live in the UK. A very simple 2D vector costing a few bytes could show the UK as a right angled triangle at minimum zoom. But no, got no 4G? Sucks to be you. You just see a grid. Why is there zero caching of any sorts in Maps apps, which presumably consume millions of gigabytes of bandwidth every day in traffic, and countless amounts of energy polling the same imagery twice?