It's even funnier thing actually, RN ships don't have ASuW missiles because they did had murican Harpoons, but they were retired in 2018 due to being obsolete. With no replacement, they are promising it for 2028 (unlikely) so currently RN ship wanting to shot enemy ship must close to the gun range. They did bought some Norwegian ASuW system recently but it's only been fit to few ships at most and was not tested, it's also a short range system.
Some harpoon missiles retired from RN most likely did arrived in Ukraine, where they had so huge success as using two to hit a tugboat.
I find it funny that unofficial armies (guerrillas?) are able to go toe to toe with state militaries, holding their own incredibly well, while said state militaries struggle so much. Why is that?
New technology is shifting the balance of power. Stuff like drones didn't exist until fairly recently, and western military doctrine doesn't account for them. Drones are very cheap to produce, costing mere thousands of dollars, and they're difficult to intercept. This piece of technology pretty much invalidates the whole US air defence strategy. It's simply not cost effective to use million dollar missiles to intercept cheap drones.
Quite possibly, missiles do have a shelf life and theirs might not be functional at this point or even worse could be unsafe to use as they could blow up prematurely.