I'm reading this article today and came across this quote:
So my question is this - why have they not always done this? The crew of the Columbia perished because NASA did not have the foresight to plan ahead for a mishap. I can't be the only person who has this opinion. I've felt this way about the shuttle program since I was a kid.The telescope’s unusually high orbit had placed the shuttle and its crew at increased risk and, because of the lack of a refuge, prompted NASA to keep a rescue ship on standby until the end of the 11-day flight.