The Union pushed for it because they claimed the new Company promised to come back to the table for significant QOL gains (Letter 2) after the contract was signed. It was a joke then and even more so now.

If a trip is unproductive (under an avg 5.5-7 hours credit per day) which 70% are in open time simply don’t pick it up, duty rigs only cover up for those things. They keep canceling flights for staffing sooner or later United will feel it and things will change.