No one is completely healthy in the NFL except maybe kickers.
I get what you are saying, but it is a fine line between can you go and are you a weakling for sitting out. It is the last piece of what goes into being able to play in the NFL, your thresh hold for pain. Talent, size, heart, intelligence all play a big role. Can you play with pain matters. If you said 'you can not play if you are in pain or hurt', i doubt you could field one team by this time of year.