Flame Resistant

Can somebody explain to me why I should be concerned about my children catching on fire while they sleep?
Since my son was a baby, I have observed that children's pajamas advertise their fabric as being Flame Resistant. If they are irresponsible enough to craft pajamas out of fabric that can catch fire, they warn parents that the pajamas should be worn "snug fitting". This is code for: "Wear pajamas as a second layer of skin, and good luck ever getting your child's limbs in the sleeves, and too bad their tummy is already showing in their brand new pajamas." To avoid this, pajamas must be purchased three sizes too large- if you can sleep at night due to such negligence... But what if my child catches on fire in the night, because they aren't wearing snug fitting pajamas?
I do not want my children to catch fire while they sleep, but I do have a few questions regarding this code:
1. Why are my children going to catch fire while they sleep?
2. Play clothes do not come with such warnings. Is the risk of my children catching fire greater while they sleep than when they are awake?
3. If there is a fire in the night, do snug fitting pajamas = a greater chance of survival?
4. Why aren't my pajamas Flame Resistant? Should they be "snug fitting" also?
5. Have these efforts actually reduced deaths caused by a fire?
6. Am I alone in pondering these thoughts?
7. Can somebody enlighten me?