They don't want practical ground support platforms, they want hot-shot dog fighting "air superiority" planes.
They had to take them because the administration (Carter's if I recall correctly) forced them to.
During the design and prototype phase, the Air Force kept telling the designers "it has to be faster!, lots faster!"
The design crew's consultant, a Luftwaffe pilot who knocked out a huge number of tanks during WWII, kept telling them, "No, it has to be slower - at least as slow as you can make it".
The Air Force almost got permission to junk them - then there was this little unpleasantness in the Gulf.
After that, not only was junking them not allowed, but Congress started thinking about the possibility of forcing Warthog II on them.