JavaScript is simply the better term, and marketing is everything. Reminds me of Java's POJOs, which was a very simple pattern that no one used, until someone gave them a fancy name.
ECMAScript is a horrible technical name. Might as well call it ACMEScript considering how willie e. coyote it feels to develop with it...
And it would feel just the same if it was named something else.
It's just a name, who gives a damn?
This is extremely ironic given that JavaScript was so named because people do give a damn about names so Netscape/Sun leveraged the Java success to push JS, hence they named it JAVAscript despite it having nothing to do with Java.
nothing against people with eczema of course
POTS = Plain Old Telephony System COTS = Commercial Off-The-Shelf
ECMAScript is a horrible name. It's worse than Google Bard.