Slab Floor Questions

I just returned from inspecting a rancher, with a half full basement and the remainder of the home built on a slab. Home constructed in 1984, no additions. please look at the attached photos, the viewing space is extremely limited. I could only view most of this with the camera. The main water supply was obviously replaced, it now enters the front basement wall. Opinions, why is there a large gap, maybe damage from the plumbing work? The bathrooms are on the slab, well away from the area shown here. Copper water service lines for the bathrooms travel from the basement, through the attic to supply the bathrooms. I have never seen a situation like this.

We could guess why people do thing forever but it needs to be fixed.

Slab is undermined at (location), repair as needed to maintain structural integrity…protect water lines in attic from freezing and associated damage and is that PB piping?

PB is disconnected, thank you for the opinion.