It seems to me that we have a childhood legacy from being compelled, forced to say "we're sorry" in order to survive, to defuse, distract the large being confronting us in anger.
It's the best we could do at the age we were then.
And it worked well enough that many of us, including victims or abuse, still use "I'm sorry" to get by, to survive.
However, this often leaves many of us with an "allergy" to apology.
There are incidences in which we know, deep down, that our partner deserves our apology, and then we remember how badly we felt when we were younger - and we don't ever want to feel that way again.
So we choose to say nothing at all ' and our marriage or relationship bleeds, suffers.
Ultimately, the connection between us and them, fades, trust is lost, the relationship dies.
In marriages an Apology can be far more useful.
To couples I coach I say, "I choose apology not to make me feel less (as once I did as a child) but to create a space in which you and I can become more. More connected, bonded, and in Love."
A well designed and intended apology can help heal any relationship.