Something i think about is how the concept art of the game admits the pipe guns aren't meant to look like real guns, just "gun shaped". The devs did it intently :
Fallout 4-Inspired Pipe Rifle New Texture Preview at Fallout New Vegas - mods and community
I'll never laugh at .38 or pipe guns again. I never used them thinking they were weak. I was very wrong. Started a new game. Found this, modified it and close range
Pipe RIfle | Fallout 4 Wiki
Level 50 - Two Shot Pipe Rifle - Fallout 76 Xbox | eBay