"Extremely inhumane" "horrible and agonizing"....LOL. What are you trying to prove?

I've used this method many times over and not once did I observe any distress at any time during the process.

Sure, you can't regulate it, but the rate of sublimation of dry ice is so slow in normal room temperature that the concentration of CO2 doesn't build up very fast, and thats the whole idea.

Both methods can be made to work. Using dry ice is simply the "easier" way. Less set-up, equipment, etc.