Is it not rather that you can't easily tell from context whether foo is a hash or a hashref?

It's not paying attention to context. Last time I did that, I passed a reference to a named hash to a function, e.g., foo_function(\%hash), then in the function started using the argument as a hash instead of a hash reference, and inconsistently at that. And then going back to the calling function, and adding code that assumed the hash was a reference. TGFS (Thank Go(o?)d(ness)? for strict :)