They don't want to preserve Abrams building capacity. The Army not only has enough for current needs, they already have enough for every possible contingency, including: "WW3, except for some reason it's not fought with nukes but with gigantic tank battles."

Assuming the Army rotates tanks out of front line service before they are useless, by the time the fleet is too worn out, the Abrams design will be hopelessly obsolete. Not because the design is bad or obsolete, but just because that's how many of them there are.

In contrast, the Army has massive deficiencies with many of their other, lighter vehicles, and has been trying to rectify them for decades now but all the projects have failed, for various reasons. Some of the failures have been the Army's fault, but others can be traced to the Congress deciding that the Army needs more tanks to stockpile instead of, say, armored ambulances.

Honestly, what the army really needs to do is somehow push for a heavy IFV/APC design based on the Abrams chassis, similar to how the Russians have made the T-15. Not because that would be a great match for their needs, but because since the production line is apparently completely impossible to kill, might as well try to have them make something that is even marginally useful, compared to the vehicles they are building right now that just get driven from the factory to permanent stockpile where they will probably sit until they are decommissioned decades in the future.