Seems like a weird place to apply conservatism. That is, right after inventing entirely new tokens and grammar. But the keyword semantics SHALL NOT be modified.

Historically, you couldn't use ANY of them as object literal keys without risking problems. I believe it was an oversight.

JS has reserved a really long list of keywords that have been around for a long time.. I've seen this occasionally trip up new JS programmers because the words are special without having any use.

abstract, arguments, await, boolean, break, byte, case, catch, char, class, const, continue, debugger, default, delete, do, double, else, enum, eval, export, extends, false, final, finally, float, for, function, goto, if , implements, import, in, instanceof, int, interface, let, long, native, new, null, package, private, protected, public, return, short, static, super, switch, synchronized, this, throw, throws, transient, true, try, typeof, var, void, volatile, while, with, yield

Well, right, but this is JSX, not JS. The rest of JSX is also illegal in JS.