I will have to disagree with you with that. There have been lots of deaths concerning MMA fighters because of their concussion https://en.wikipedia.org/wiki/Fatalities_in_mixed_martial_arts_contests
and as for me, MMA is the most ridiculous and most brutal sport (really street fight) that the rules have to be changed to. As a boxer, you have a choice not to keep going just by quitting, not getting up when you go down, or your corner throwing the towel in. In MMA when you go down, most of the time the fight does not stop unless it was a clear knockout, but instead they keep punching when they are down and using elbows and knees till the ref says it's enough. I'm a boxer myself and had few fights, and when one of the boxers is not responding for few seconds, by punching back but is receiving the punches on the head, the ref will give you a 10 count and check if you are ready to fight. You can quit or keep going. In MMA you have no referee asking you if you are OK and if you want to keep going. Yes, you can tap out, but that is only when someone is choking you or about to break your leg or arm, not when you get punched or brutally being kneed or elbowed to your head. There have been more deaths in boxing, but that is because boxing has been here forever and MMA is pretty new so you cannot really compare. This study did show more trauma in boxing, but there are so many other studies that probably will show you different results. But we all know that the tv, and media is all controlled, they will only show you what they want you to see, and if they want to destroy boxing, then they doing a very good job. Just like you, I never heard of MMA fighter die, because they will not show it on tv, but if you check the link above, there are so many deaths.
Some people tap to strikes. Case in point, Shogun Rua vs. Jon Jones. I think most of the deaths are the weak regulations in place since it's still a young sport.
mma fighters can def tap to strikes
myself I like both sports, truthfully I like all combat sports that I know of