Ask HN: Why do I never read about “Masers?”

Microwave Amplification by Stimulated Emission of Radiation (Maser) is the precursor to the Light Amplification by Stimulated Emission of Radiation. It is used for atomic clocks and is basically the same device now that it was in the 1950s.

Is there anything new or interesting regarding this device or is it a sort of "vacuum tube circuit" in terms of limitation of iteration?

https://en.wikipedia.org/wiki/Maser?wprov=sfla1