Jimmy- i have triplets (age 4) who say "I'm sorry" all the time. I get worried that teachers think I make them apologize when it's the exact opposite. My kids are repeating what I say (2 are on the autism spectrum and that's a common trait) . I am so quick to apologize when I make a mistake with them. I absolutely hated not being validated when my parents were in the wrong or accused me unfairly of something I didn't do.

I also realized after having children why my parents did things I thought were so wrong. Not saying they weren't wrong, I just have more of a understanding now. Its helped me do things in a different way than my parents.
Ex- my son was taking a bath and I stopped the water bcc the tub was full. I went to check on the other two when I heard the water turn back on. I ran in and yelled at him, "why did you do that? I said no more water!" He started crying so I sat down and explained that the water can get really hot and burn him. I said I would be really sad if he was hurt, that made me scared. I apologized for yelling and he calmed down.
I always got yelled at with no explanation why. I realize now that's had a huge negative impact on me and I don't want them to go through that!
I agree with you that books and all that has its place in parenting. However I feel when I think of what I would've wanted instead of just doing what I saw growing up, acting on that seems to yield the best results with happier kids.