If the idea of execution is to serve as a deterrent to make other, potential, criminals to stop and think before they do something stupid, why the attempt to make the execution “more comfy”? After all, they’re going to be dead in a few minutes anyway. If you really want to deter someone, make the penalty as horrific as possible...make it a teachable moment that is going to give people pause.
I have never viewed it as a deterrent but as a way to protect society from people who kill without remorse or conscience. Life in prison means they have nothing to lose by killing other inmates or guards.