“You are supposed to pay your taxes”

This could mean that you should pay your taxes, under obligation. What can I tell you? What can a speaker mean about me assuming he/she pays his taxes?

“You are expected to pay your taxes”

Again, this could mean that you should pay your taxes, under obligation. Could be just as well that nobody (probably the speaker) has presumed that you pay tax.

Why do some people really feel the double meaning of ‘expect’ and ‘attend’? The presumptive meaning of “suppose” is rare in modern English, so this parallel hasn’t been obvious to me until recently.

Why do there two different words corresponding to the same meaning?

Why do I need my education like zzz?