because of the Job of being a Demon slayer and the Public not knowing about it. The Hashira or Slayers get arrested from time to time for carrying a Katana or for slaying a demon and the police thought it was a normal human

Giyuu Tomioka the Water Hashira was arrested and walking through the little village with his hands in a rope and his blue eyes roaming the town.

eventually he got annoyed and he broke the ropes with his raw strength.