And that in turn would also be "it's what they have, not what they want to use", as these would be rather expensive and overly large drones. Something like 75% of "drone magic" effect people see now is that many drones are practically semi-stealth aircraft out of their unusually small size and speed (in comparison to the average tac jet), messing with some less capable and less professionally operated air defense systems with this alone.
And why would we limit ourselves like that to not exactly the greatest supplier?
JA37 was obsolete in 1990 when its production ended, it would be stupid to buy it afterwards, worse than the old Mig-29's we have.
As for Grippen, we couldn't afford a main fighter with no NATO supplier and less than 300 in operation - we would have no idea if, when and what upgrades and spare parts will be available, and if we could get more during a war. As opposed to F-16, the most common of NATO fighters, built in thousands, with hundreds of whole spare fighters standing in American desert.