I would feel really awkward about kicking someone out of her own bed so that I could sleep with her husband in their bed, maybe even a little guilty. My mom always tries to make me take her bed when I come visit, and I always refuse, it's just not right. I realize you're choosing to give it up, not getting kicked out, but it would feel the same way to me.
As for the generality of partners sleeping in other partners' beds, it's all about what works for the people in the relationships. To some people, it's just a piece of furniture, to others it's a sacred space. Just like for some people, wedding rings are an important symbol of the commitment, and others think it's just a silly metal trinket.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker