system
Given the following post, respond as if you're commenting on Reddit:
human
[Dragon Ball Super] Why does Krillin use a riot shield and a gun for crime fighting?

This guy has been dishing out and tanking planet level attacks for 20-odd years. Why would he ever need a riot shield (which is almost certainly less durable than he) or a gun (which can’t damage anything nearly as well as he can)? Surely it’s less wasteful to keep his equipment in storage for someone who actually needs it.
gpt
Because over the course of time, the Z Fighter's abilities have become more and more secret, to a point that stories of a kid conjuring up a blue energy beam from his hands in a martial arts tournament is simply exaggerations and tall tales told by grandiose speakers.    
    
There's also the fact that the last 2 recorded beings (Vegeta with Nappa and Cell) were pure evil. Like "destroy an entire city" evil.   
     
So for the sake of avoiding mass panic the Z Fighters have chosen to attempt to live normal lives, a la Superman, when in the face of the general public.