I tend to like my steaks medium rare to medium, depending on the venue. I think it has to do with flavor, mouth feel, tenderness, and juiciness. The short answer seems to be that it tastes better to some people. Could there be another, more primal, reason for this? A taste for blood perhaps?
Some people like theirs well done. IMO, that defeats the purpose of having a steak. One can get well done meat in burgers, roasts, meatloaves, and briskets that are cooked to the point of being well done.
I guess a secondary question could be “Why do people like their steaks well done”. Personal taste is, by definition, subjective. I’m looking for something scientific that might explain a proclivity towards meat that is cooked to a lesser degree, and greater degree in regards to the second question.