A major issue with solar thermal is clouds and dust. PV works fine with indirect light from a dusty panel, but to concentrate sunlight you need a clear sky and clean surfaces. Next you need 2 axis solar tracking to get high grade heat or a complex trough system with a separate working fluid and complex plumbing/heat loss. Next you lose energy trying to concentrate sunlight and from the heat engine itself.

In the end it seems like it should be cheap but nobody got it anywhere lose to PV pricing.