For one thing, because the parent you were responding to did not make that distinction, and it wasn't clear why you chose to make it. For another thing, limiting US defense space activity spending to just the Space Force budget is naive. All departments of the military operate space activities, and have not and will not hand all of that over to the Space Force (see also: military intelligence vs CIA). We can't know the exact budgetary amounts of each department, and then there's the NRO (National Reconnaissance Office, managing space-based spying), infamous for donating [1] its obsolete telescopes to NASA, which were of comparable performance to Hubble.
[1] https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...