You say that with zero context. Did you actually tell them what happened? Did an assault actually occur?
Every officer has to work in perameters set up by whatever state they are in, and "take them to jail" isn't an automatic button. Sometimes disputes are civil, to which honestly an officer can't do anything except either separate the parties for the night or tell everyone to calm down. Police are reactionary by the nature of their job. Officer's aren't even the ones who press charges, district attorneys/assistant district attorneys are. Each department does it slightly different, but a DA/ADA has to accept the charge, and sometimes they wot based on certain information.
I had a mom and stepdad who were clearly abusing a child, left him alone for countless hours, and never fed him. I was able to get "Abandoning a child" on the stepdad because he had last custody of the child, but I had nothing on the mom who was clearly ten times worse than the stepdad, because the ADA wouldn't take charges due to the boy's bruises being too old. Instead, I took the kid to CPS, but I've been told they gave him back.
Sometimes we straight up can't do the things we want to. That's why usually I lay out laws or quote penal codes to people so they don't have the mentality like you do, and understand that I can only do so much.