How best to explain? You are some second or third level air force, with a limited budget, you want a new fighter. (If any of your potential enemies have supersonic fighters, you could maybe use one, if not, a good armed trainer like the Hawk 100/200).
But no....you want a big manly top of the range F-16, like the big boys have.
Or maybe you do need a cheapish fighter, the F-20 is made for you, at this time in the 1980's it's weapon options are as good as most F-16's.
But no....the USAF and NATO has F-16's, so you've gotta have 'em. Never mind the F-20 will be easier and cheaper to maintain, important factors in combat.
Imagine these guys like South Park's Eric Cartman, 'I wanna F-16 dammit!'