Because, at the time, a satellite launch cost a phenomenal amount, took about a year to plan and launch, and gave you (at best) one pass a day which stood a good chance of being obscured by weather, and didn’t have brilliant resolution compared to an aircraft..
And why the sky sky is now crowded with 24/48 hour endurance recce drones such as the RQ-4 Global Hawk and RQ-170 sentinel rather than depending on LEO satellites.