“The real answer might just be: Because God said so… “
That is the correct answer, Jewess. The only question is why did G-d say so? We can try to figure it out until the end of time, but at the end of the day, because G-d said so is the only answer we need to know. I guess we are not meant to know everything. Even if fish did not feel pain as we do (and as far as I know, no fish, even the Talking One, has ever told us whether or not this is true), it still has to be scary to smother to death unable to breathe. The fact that they are flapping around kind of indicates to me that they are not so calmly accepting of death. And now, I will not be able to eat fish for a while.