Why do some parents use children as a way of controlling (or trying to!) their ex?

[namechanged123123]

Name changed as this will be a divisive one!

There's be a load of threads recently whereby one parent is clearly using children as a way to 'control' or 'have an influence' on the other parent's life, and I'm just curious to those who have done that how they justify that when it's clearly not in the best interests of the child...

Some vague examples of comments or threads I've seen
-NRP not paying sufficient maintenance
-Mum/Dad not happy with children meeting and/or spending time with ex's new partner
-RP saying that the time the NRP is for NRP only and shouldn't spend time with anyone else in that time
-Mum/Dad interfering with new half siblings relationships
-I've actually seen numerous posts on here saying that if you separate with child's other parent you must remain single until they are grown up
-NRP changing contact arrangements last minute or reducing contact when they have a new family

I can't be the only person who thinks none of this does the children any good and actually it's so important for them to see healthy relationships between the adults in their lives?

Difficult for healthy relationships to be modelled when they may not exist. Why should you try to maintain a healthy relationship with someone who has hurt or abused you, physically or emotionally?

This is a thread about a thread.

In my experience NRPs can be very controlling. For example by not contributing financially meaning the RP cannot afford to work full time, not taking care of the children for anything more than a few hours at a time, stopping seeing the kids when the parents use CMS. I could go on.

This is one thing I REALLY cannot stand.

I cannot understand why parents cannot see when their behaviour is not in the best interests of their child.

I think part of the problem is each parent feel they are the 'worse off' party. For example the NRP feels they are worse off through not seeing their children every day and paying money that they perceive as supporting the RP. The RP feels they are worse off as they are constricted in their career due to childcare and feel they do the day to day slog but get less fun with the children.

In actual fact if both parents took a step back, removed their dislike for each other and just let each other parent as they wished (obviously not in cases of abuse) everyone would be better off.

Me and my ex decided immediately we would not interfere in each other's time with our DD. He has introduced a string of girlfriends which i dont agree with but I never said anything and was super positive with DD about them. I'm sure I've also done things that he has disagreed with but he kept quiet. We get on better than most ex's, are able to discuss serious issues and DD has dealt with it all very well (she has recently said thanks for not putting her through some of the stuff she watches her friends go through)