(Also, it is a serious overstatement to attribute Java and C# to PL theorists. Gilad Bracha is not James Gosling. PL theorists have contributed to some extensions to these languages. Typically, the extensions that confuse people and make them feel stupid.)
The difference between the foundation and a foundation is enormous, because (with your very large expensive foundation) you are asking programmers either to program without knowing the foundations of their work, or to learn a large and challenging body of mathematics.
And you know, higher-order typed programming is good enough that it's almost worth it. For most potential customers, however, learning PL theory does not seem to be worth it. Nor are they comfortable in programming in Haskell, a very powerful and complex environment, without understanding it.
It's this "the customer is just wrong" attitude that makes some of us sense an area ripe for disruption. Pride goeth before a fall.