I actually do martial arts.
The differnce rugby and professional boxing, is Rugby the prime objective in a tackle is to stop advancement, and try an turn the ball over. In boxing, you are trying to know the guy out. Yes point are important, but you want the end the fight.
Dangerous play like tacking high, tackling someone in that air, stamping is rightly penalised. Teams can't afford player off the field.
"Hospital passes" exist is various codes, but you are aware of what will happen with training.
If you are worried about jolts to the brain, take the pads an protection off. Pads cause more shock injuries.
Scrum caps are different, becuase they are protecting the ears.
One of the myths is boxer wear gloves. In order to protect the person they are hitting. Nope. Wrapping the wrist mean they can hit an bad angle not possible in bare knuckle without damaging the wrist. Gloves enable to you to hit harder on the hard targets.
American football they head barge at full tilt, do that without neck and head protection and you will kill yourself at that same force, or become paraplegic.
That is why the head is tucked in rugby and you have to attempt to get the arms round or it is not a tackle.
Technique, and good supervision is essential.