I think they do on many occasions...as soon as they go down its like ref jumps in and waves it over if a KD punch has landed...no counts etc like in boxing.
Another MMA thread on a boxing forum. You have to remember that in MMA, if you knock your opponent down you can then mount him and start either rolling around on top of him or punch them when they are unable to protect themselves. For this reason you have to stop the fight to protect the injured fighter from taking "man loving" on the canvas.
Maybe some... not too many. You have to remember that in MMA, if you get knocked down, your opponent is going to pounce on you and finish you.... so normally the fighters doesn't have time to recover, like in boxing. There is no 10 count to allow him to regain himself. It just depends on how heavy they go down... if they go down cold... then the fight is being stopped to save that fighter from second impact syndrome when his opponent starts nailing his unconscious body.
Some fights might be stopped too soon but that is better than too late. Any person with an understanding of human anatomy and physiology knows that standing a guy up and giving him 10 seconds to "recover" from semi-consciousness is VERY bad for the brain if he resumes taking a beating. I think it is safe to say that the long term effects that many boxers endure will be lesser among MMAers because of the stoppage and tapping rules. Of course, only time will tell.
There was an interview with Steve Mazzagati after the Mir/Lesnar fight where he discusses stoppages. He said that stoppages are based on the class of fighters. Look at the Serra-GSP stoppage for example. In championship fights, they let it go on until it is VERY VERY clear that the fighter can no longer defend himself. With lesser fighters, they are more inclined to stop the fight earlier.
this might explain why many mma guys are still elite and apparently mentally fine in their 40's (couture, henderson, ) whereas a guy like hoplkins is an exceeption and most boxers are showing significant mental decline at an early age....
Because of the range of techniques available in MMA, fighters are generally able to avoid the prolonged beatings that boxers endure during boxing. The large gloves and rules exacerbate the internal damage taken by the average boxer. By "rules" I mean that the only way to win is to basically beat the other guy's brains in. In MMA, the rules allow for a variety of victories so it is possible for a fight to lack a single punch even being thrown. In that regard, MMA is inherently safer than boxing and kickboxing.