Generally it’s a combination of a lot of the headline equipment being 90s era, and the systems themselves being sent in order of oldest first. While yes, these were very much a part of our arsenal, and yes we often them stockpiled for a reason, sometimes that reason is just that the US military rarely throws anything away until it absolutely has to. When it’s actually being replaced however, it’s generally because those parts of the stockpile are meant to be used as a stopgap. Production lines tend to take a long time to spin up and so we keep a reserve supply of things on hand to cover the gap between when a major war might start by surprise and when the new assembly lines to supply it are finished.

It is however worth noting that most weapons built in the last fifty years use would fuel propellants with a limited shelf life before they become to dangerous to handle. As such, if you want to keep a constant stockpile you must constantly be building new rounds and decommissioning the old ones at the end of thier life. Moreover tech has actually advanced between now and then, and many of these new versions are more effective, if expensive, than the old and so need to be replaced a way.

In some categories we are indeed sending more than we normally decommission, and so need to increase the rate of production to even things out again, but that’s not how congress has been primarily budgeting things. Instead the headline figure, when not double or triple counted, is cost to replace old system with an brand new equivalent worth of old system irrespective of wether or not it was due to be replaced anyway.

All of this is a bit harder to separate from general defense spending however because we were already beginning to pivot from counter terror operations towards the asia pacific in order to provide a credible deterance around Taiwan since China has been rapidly expanding the PLA and PLN while many politicians have been using increasing imperialist rhetoric to distract from domestic trouble.

So anyway, that’s my guess as to why people thing were sending old stuff we found in a stockpile somewhere.