Mine is a bit like @thorninmud…our communication style is so different, I refer to my MIL as an alien when discussing the situation with my family/husband. She and the FIL are extremely literal people. I express more emotion than either of them can stand.
In the past, my husband & I put in great effort to try to relationship build with them. We have discovered that they prefer their hermit-ish life style of no friends, rare visits, and little to no “going out”.
Since my husband & I are attempting to have as many good social role models around our son, we have mostly cut his parents out of the equation at this point.
As to your why @jca…In my personal experience it is due to extreme personality differences. I think I’m one of the first in my family to experience anything like it. Most of the generations before me lived with in laws in their homes or on their properties. My husband & I have my mom living with us…he gets along fine w/her.