Let became optional quickly it seems

But most BASIC versions would accept 'let a = 1'

Personally, I don't see why the big fuss. If your assignment and comparison operators are the same the only thing you lose is doing x = (y == 2); kind of expressions (since you would disambiguate from conditional expressions).

Now, assignments are done more frequently than comparisons, hence why it makes sense for it to be the simpler/shorter one.

You wouldn't even lose that if you can accept that assignments can't be expressions, which seems like a bit less of a loss.

> And most BASICs, though some (most?) required the keyword LET to introduce an assignment, as well.

LET was virtually always optional; an expression by itself on a line (like 'X <> 10') is a syntax error anyway, so removing LET doesn't introduce any ambiguity.