If they could have 1,000 asat sats, they'd want to have 1,000. Can you imagine them saying "sure, let's just have an X-37B, one, just one, it will do"? If you need these in a shooting war, 1 ain't gonna be enough. You need lots of them. You can't have lots of them if: they're big and heavy (launches are too infrequent and too expensive) or if they're too expensive (you want 1,000 but can only afford 10).
If they could have 1,000 asat sats, they'd want to have 1,000. Can you imagine them saying "sure, let's just have an X-37B, one, just one, it will do"? If you need these in a shooting war, 1 ain't gonna be enough. You need lots of them. You can't have lots of them if: they're big and heavy (launches are too infrequent and too expensive) or if they're too expensive (you want 1,000 but can only afford 10).