Realtime Java: A Real Alternative to C and C++ for Programming Embedded Systems

Whereas cloud and desktop computing has moved on, embedded systems are typically programmed in C and C++. One sees some use of Java, Java Script, Scala, Python, and other managed languages, but their penetration is small. Managed languages have contributed to a drastic increase in productivity for cloud systems, one might ask, why are managed languages not more prevalent in embedded systems?