Eh, I actually like JS but I have definitely forgotten to add a "var" or "let" a few times, or sometimes I will do it correctly, get a bit overzealous with cutting, and accidentally remove the initial var declaration.

I'm not saying that it breaks the language, but it definitely is irritating, especially if you're not using a linter.

I come from Lua so I'm used to declaring local variables with "local".

Also, I like knowing which variables won't be reassigned (const), and which will (let).

Whilst I do find it irritating, I don't mind about the scope default so much, but I've certainly run into it (forgetting to specify) a lot.

Mostly because JS is not the only language that I'll be working with at a time, and if I'm dancing between three or four and they have similar syntax, then mistakes creep in.

That's all fine, but those are all workarounds for a design mistake in the language.

No it's a choice, apparently people can't have one.