Q: Why do match expression need parenthesis for ops to the right but not left?

This is probably a somewhat stupid question, but why does match (or if for that mapneed a statement form at all? Why can't it just be expression whose value is discarded if used with a ;?

Do things like

let foo;
match bar {
    Some(_) => foo = 1;
    None => foo = 0;
}
// foo is now initialized

not work with expressions? I suppose I've never tried, but I don't immediately see a strong reason they couldn't.

EDIT: sorry I've realized I just answered my own question, it's so that they can used without a ; that they have a statement form, I got tripped up by the context.