Old married couples argue a lot. You know the ones I mean.
Especially if your parents argued a LOT and never got divorced even though they wanted to get divorced but "stayed together for the kids". Then you will know what I mean on an intimate level because it happened to you.
But I have to wonder which is more traumatic for a child:
1) Getting a divorce.
2) Staying together and putting your kids through hell as you argue constantly.
Option 2 could even include spousal abuse, which means the children might be witnessing all manner of spouse on spouse violence - and growing up might continue that cycle of violence with their own spouse.
Any kind of spousal abuse is immediate grounds for divorce in my book. Regardless of who the victim of the abuse is, they should also make efforts to document the abuse with photos, video and visiting a doctor, and police.
And back up photos / videos online so the spouse cannot delete them. Quick and easy way to do that is to email the files to a friend or family member for safekeeping. Or multiple friends / family members.
Anyway, even without abuse you need to be thinking "What is the effect of all this arguing on the children?"
Well it is traumatizing to say the least. To the point that children sometimes run away, attempt suicide due to stress, get into drugs or alcohol, develop severe depression, become violent and act out, etc. I don't have any scientific studies to back this up, this is just my observations based on years of witnessing various parents who probably should not be together and argue so much their kids are traumatized.
It would be very interesting to see a scientific study done on the topic. It is possible there is several studies on the topic, so feel free to try and find one and then post the link in the comments.