Same with the F/A-18.

I remember being really into naval aviation when I was a kid, and I'd look at carrier air wings. There would be F-14s for air superiority, A-7s for light attack, A-6s for heavy attack, EA-6Bs for electronic warfare, KA-6Ds for tankers, S-3Bs for anti-submarine warfare, etc.

Now I look at a modern carrier air wing, and it's F/A-18E/Fs for air superiority, F/A-18E/Fs for light attack, F/A-18E/Fs for heavy attack, F/A-18E/Fs for anti-submarine, F/A-18E/Fs for tanking, and EA-18Gs for electronic warfare. Same for the Marine Corps and a bunch of foreign nations.

For that matter, the X-29 was itself a variant of the F-5, another lightweight, low-cost design that got a lot of mileage in different roles, including being the starting point for the F/A-18 design. Sometimes it pays to be cheap.

Yeah, plus it had been a huge success in the foreign military sales market. So any F-16 2.0 that got traction was a product they could potentially sell to dozens of countries, even if the U.S. Air Force never bought it.