Let's look at X and Y. Suppose a one earner couple has an average indexed lifetime wage of $98,400. That leads to a PIA of approximately $32,000 (annually).
If the spouses are the same age and both start at NRA, they get a combined $48,000 while they are both alive, and either would get $32,000 after the first death.
Now look at two single people each earning $49,200. Each would have a PIA of about $22,000. So, they would get a combined $44,000 while they are both alive, and either would get $22,000 after the first death.
I'm having trouble figuring out why the married couple should have the extra income.
Yes, I can see that married people don't want the same benefits that single people get.* So, my idea is "wild and crazy" in the sense that it is a political nonstarter. But, I'm not a politician, so I can say politically unpopular things.
*Tthat's a benefit cut even for the simple case where people stay married. When we get into survivors benefits on ex's earnings, the extra benefit gets even bigger.