What do you mean "we have to go somewhere else to implement simple things like FiSH"? As I pointed out in my previous reply, you can implement it in mIRC; simply. In fact, it's already implemented in a few scripts. Scripts like Mircryption
already exist for mIRC and implement Fish without modifying the binary, and there's the less-recommended "FiSH" patch available as well (recently updated for 6.35). The focus here isn't whether or not you can use FiSH with mIRC (you already can), the issue is whether it is worth Khaled's time to re-implement already-existing scripts inside mIRC for the very few users who use them.
If you know many networks that use FiSH, please list them. I'm not quizzing you, I'm genuinely interested to know which networks implement this encryption scheme.