Why SH3 ...

[AVGWarhawk]

Boring torpedoes. Manual targetting was ok in SH3, and mods have made it a very strong point of SH3 (strongest IMO). But the torpedoes are much too reliable (=boring). They can detonate too early, ok. But that's it. They maintain depth perfectly, they can breech the surface in rough weather and keep going straight like nothing is happening, they don't deviate one bit from their course (not even an abstract representation of sea currents).
If you read on Prien's attack of Scapa Flow, only 2 out of 7 torpedoes hit the static targets. He says "The torpedo misses I explain due to faults of course, speed, and drift. In tube 4, a misfire."

SH4 had this with exception of current affecting the torps. I hope that found it's way in.