Not pulling out of fights is certainly a good attribute to consider.
It relates to durability, smart training and heart(or foolishness).
Sure, pulling out once or twice due to freak injury is ok but someone who does it constantly definitely raises red flags. Also, not many people are able to go through their whole careers without pulling out so it does mean a lot when those few who do are able to do it.
You guys can't say it means nothing then go and shit on fighters like Cain for pulling out constantly.