Compiling expressive syntax through a powerful optimizing compiler to produce binaries run by microcontrollers is really sweet. Definitely the way to go, if you want to get the most functionality from limited hardware, without going all the way to assembly.
I guess JavaScript could be good for people who want to do very simple things, and then invest lots of time fighting limitations as their ambitions grow, rather than learning something useful. Like people do with Excel.
Which brings me to my next question: why not take it to the limit, and make microcontrollers programmable purely in Excel macros? That would be maximally accessible. Lots of people know Excel and can’t get enough pain.