It wasn't just pressure to launch a teacher. Part of the arguments NASA had made to secure funding for the shuttle program had hinged on the claim they could launch on reliable schedules. The military wanted more funding for unmanned rockets to launch satellites, but NASA had prevailed in Congress partly by asserting that the shuttles could put military hardware into space, replacing the need for more or newer unmanned boosters. The military was dubious they could maintain tight schedules and launch on short notice.

NASA felt pressure to prove their program could get into space regularly with minimal delays/cancellations in order to justify the spending and prove the military "wrong."