> Why are they trying to retrofit an F16

Because there are lots of them,

As of 2023, it is the world's most common fixed-wing aircraft in military service, with 2145 F-16s operational. [1]

and several countries are phasing them out in favor of the F35. Pilot training is a slow and expensive affair (ask Ukraine), so it makes sense to concentrate scarce resources on the top model - unless the legacy one can fly itself.

[1] https://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting...

Do you know how much time passes between "let's make a whole new platform without human-required accommodations" to an even an aerodynamic model? Not even talking about the first flight.

If you have a bunch of cars sitting in your garage and you want to test your auto-driving software, you don't start by building a car. Simple as that.