I hate the idea of something breaking right after I sell and making me look like I didn't disclose something. It's just uncomfortable.
I remember when we sold our house in St. Louis and I was driving through the middle of rural Kansas on my way west when I got a call from the new owners of our home. They had just finished piling a bunch of still-to-be-unpacked boxes in the basement when the basement floor drain backed up and flooded.
They wanted to know if I was aware of any plumbing issue, and while I assured them I wasn't, it was a very awkward conversation. Had I purchased a home warranty, I'd still feel bad for them, but I would feel less responsible.