Why are Octal numeric literals not allowed in strict mode (and what is the workaround?)

Question

Why are Octal numeric literals not allowed in JavaScript strict mode? What is the harm?

Answer 1

Nowadays, with large browser support to ES6, you could write this:

const NINE = 0o11; // octal
const TEN = 0b1010; // binary
const SEVENTEEN = 0x11; // hexa