The first reason is, people who build tools mostly don't think that the tools will or should be used as components of other tools for more in 'automation'. The result is that it's tough to build on such tools.

The second, and more specific, reason is that location of one of my most intense love/hate dilemmas, Xerox PARC that pushed the first 'graphical user interface' (GUI) instead of what came before, usually typing text into a command line. Command lines are mostly easy to automate. GUIs are mostly a total PAIN to automate.

I'm wanting to automate, willing to automate, waiting to automate.