It isn't really a big deal. These people lose their fights and the sport moves on. Promoters don't call them back, they find something else to do with their lives. Somehow they made it there and they surrendered. It's not like the Klitschko/Povetkin hugfest if you have a problem with that.
I think upkicking & defending takedown attempts with knees to 'grounded' opponents should be legal.
Favs.: Lawler, Rumble, McGregor, Velasquez, Werdum, Machida, Pettis, MacDonald, Dodson, Fedor