If you served in the military then you ought to know better. How many UAVs do you think we have airborne at any given time? Those people came in separate vehicles. Suppose we'd done nothing like you suggest since we were not 100% certain and they went separate directions. Which car would you follow?

There aren't very many UAVs in the AO to start with and several have been lost in operations. Furthermore, those UAVs are designed for a particular on-duty/maintenance cycle. Once a UAV returns from a mission (lasting up to 24 hours), there's a certain amount of maintenance required before it's ready to fly again. There are also limitations on the number of vehicle command and data downlink systems available in the AO. You can't just launch everything to cover a single meeting and hope to keep all of those targets in sight until the time when we'd be 100% certain about their identity and intentions.

Tell me, since you seem to think we can't do anything unless we're 100% certain of the outcome, would you want to apply that standard to other government activities?