Because I sure the heck don't know. Maybe it's like watching a train wreck in slow motion. Every relationship between individuals and within groups is dysfunctional. Husband/wife, brother/sister, brother/brother, stepparent/stepchild, current husband/ex-husband, colleague/colleague... all of them. Not just in the families of the victims, but even more in the lead detective's family. The rudeness quotient is off the chart. Anytime anyone opens their mouth, a lie comes out or an f-bomb, or both. And approximately one million times in each episode, someone asks someone else, "Are you okay?" and the person being asked always says, "Yes, I'm fine" even though fine is absolutely the very last thing they are. This applies to the cops as well as the victim's family. Why do I keep watching it? I guess because I live far from any railroad tracks.
Interesting note: the first two episodes of season 5 were directed by Shaun Evans who played "Endeavour" in the brilliantly written series of that name that wrapped up in July 2023. I assume Shaun is now at loose ends. "The Bay" doesn't come close to the level of quality that "Endeavour"maintained throughout its run (except for season 7, which was embarrassingly bad).