My wife is 1 of 13 kids. With a minimum of 3 psychos.
My in-laws don't have a trust/will. FIL isn't the "let's sit down and figure it out so there's less problems later" type.
There won't be much to divvy out anyway, but the "things" will cause problems.
For example, nobody but my wife does family history in her family, and there's a lot to be done on my MIL's side. You'd think that if you have someone in your family actively doing that, you'd let them have all that stuff, or at least borrow it so they can complete it. Nope. A single/no kids Uncle passed away, and one sister decided she wanted all of his family history stuff.
Might as well light it up.