An old saying in aviation: it's better to be on the ground wishing you were up in the air then to be in the air wishing you were on the ground.
As I headed to the side of the road to watch the Astrovan drive by a gent next to me said "They ain't going." Two heaters on an APU had failed, the weather at the trans-atlantic abort sites wasn't good, and the winds here at KSC showed no signs of dying off.
Sure enough, from the side of the road we watched the van pull into the LCC, and sit... and sit... We waited, and when it came out instead of turning left toward the pad it turned right, back to the crew quarters.
Especially with the Shuttle, it's better to be on the ground....