Because it says "I don't accept that you are this child's full, and only legal, parents, and I want to use legal means to take control away from you, and put you in your place. I don't accept that you will be acting in the child's best interests."
The harsh reality is that Miracle couldn't parent her son at that time, and he needed new parents. Taking person's parents to court because something is happening she doesn't like undermines any trust that's being built between her, and the parents who are doing the graft of raising her son. She posts gratitude about these people, taking them to court does not demonstrate gratitude, it will push them away.
Adopters are just normal parents. Any parent threatened with court about their children would hunker down. Imagine a distant aunt threatening you with court for being slow with the Christmas card update on the kids - it's nuclear, and severs, rather than builds, trust and relationships.
As an adopter, as a mum, I know my kids best. If I see it's best for them if contact content or timing changes, then I am the one who makes that decision, legally, we are the parents. It may not be necessary, or in their best interests too share why changes need to be made. These children are scarred by their experiences, and adoptive parents can be protective. There is usually good reason children are adopted in the first place, after all. If the birth parents took us to court, they're saying they don't trust us, and they know better than the people raising the children, and want to force the parents of the children to do something those parents have said no to. In that situation, I would do exactly what I was being forced to do, to the letter. The goodwill would be gone.