Bush didn't qualify on just any fighter aircraft, either. He qualified on the 102, a flying coffin held together by bailing wire and spit. The 102 "Delta Dagger" was one of the last Century Series fighters designed by Convair Aviation for Interceptor missions. The 102 was not, technically, a fighter. It was designed to intercept Soviet Tupolev "Bear" bombers flying over the Pole to targets in the CONUS. It first flew in 1952, and was part of our air cap during the Airborne Alert era of the 1950's. It's job was to keep the Bears from getting close to the SAC bomber bases before the BUFF's and the B-47's could get airborne and out of Dodge.
By the late sixties, the 102 was well past its prime as an aircraft, and I'm sure that spare parts were hard to get for both that aircraft and the 106 "Delta Dart" variant.
The mission of the Texas Air Guard, at the time, was to basically fly air security over the Gulf. You'll recall that the Soviets had a naval and air base in Cuba at the time, even though much wasn't said about it. This was a long time before the Air Force adopted a "total force" package that would see Air reserve units folded into parent active wings during wartime.
Bush lost two collegues due to accidents in the 102 during his time in the Squadron. Would I be happier if he had qualified on ThunderThuds and flew Route Package missions up to Thud Ridge and Downtown? Sure. Any Republican would. Makes for a better resume. But qualifying on the 102 and surviving beats skiing moguls and pouring concrete with a bad back anytime.