To add some context to the other answers...
Ejection is not a safe thing to do.
The two most popular ejection systems today, the ACES II and Martin-Baker, have around a 90-92% success rate... the definition of success being the person lived. Most ejections result in some injury to the person, as it is a fairly violent activity, with a brief 20g impact when the seat fires.
Almost all ejection occupants will suffer some form of spinal compression, typically they'll lose half an inch of height. If the person doesn't follow protocol exactly, they may lose an arm on the way out. If the head isn't perfectly in line with the spine, the neck can be broken.
Ejection is a measure of last resort, to be used only if the only other option is certain death.
So it's pretty much a given if the crew member fires the ejection seat, there is no other viable option, and the aircraft is uncontrollable, or will very soon be uncontrollable, by a pilot or an autopilot.
Also, if the aircraft is gyrating wildly, the seat can malfunction, or the occupant can be struck by parts of the aircraft, so waiting until the aircraft is completely out of control isn't a wise move, either.