It's how any sovereign body must work. Putting something to a vote and failing demonstrates weakness, so it's avoided. And the body cannot be bound in deliberation. (Else it's not sovereign, but a vassal of whoever sets the agenda.)
Mostly agree, but often parliaments are a place to make a point to the observing voters and some things are proposed with the full knowledge that they will be rejected. The proposer though turns to the public and says: "I made a promise and I deliver, but the other side is stopping us from implementing it. So, please, vote for me next time in grater numbers to give me the ability to pass it the second time." Also, when you have a bigger assembly, last minute twists happen for unexpected reasons like a coalition partner deciding to screw their partners and ruin their agenda.
It's how any sovereign body must work. Putting something to a vote and failing demonstrates weakness, so it's avoided. And the body cannot be bound in deliberation. (Else it's not sovereign, but a vassal of whoever sets the agenda.)