The single most important gift we can give our children is a stable, two-parent, man and wife relationship. A steadfast marriage should (but often is not) be more important than the relationship between parent and child, because the success of the second is dependant upon the first. So there's the best case scenario.
In spite of a couple's best efforts--or maybe with no effort at all, it really doesn't make a difference--a marriage fails, and there are children involved. The children have already had the thing they need most taken from them. To force those kids into further instability by making them divide their time equally between two parents serves only the selfish desires of the parents, certainly not the best interest of the kids. Inherent instability! Imagine you had a career in which you had to spend two weeks in one office, then two weeks in another. Maybe those offices have a few similarities, but there are going to be some very different dynamics at play. Different physical surroundings. Different office mates. Different rules--sometimes subtley different, sometimes overtly different. That would be difficult for most adults to cope with.
So look at what you're asserting is in the best interest of a child: Two households; two neighborhoods, probably; two sets of rules; two different styles of food; two different kinds of free time. As an adult, you may want to think "Hey, that sounds exciting!" To a child, that means chaos. Add into that mix the very real fact that mommy and daddy are back on the market. Said children are then going to have a whole new set of often revolving adults flitting in and out of their lives. You want I should believe that this is good for a kid? Were you ever a kid?
Nuts!
Once again, we agree.
PLUS, this inevitably fosters in the child the idea that he has family-options. Who’s making the better offer? Mom lets me watch TV until 10; Dad makes me stop at 8. Advantage: Mom. And so forth. There’s nothing good FOR THE CHILD about that.
Plus one more should-be-DUH consideration. As a very wise person put it: “These two people couldn’t agree to stay married, but they’re going to agree about raising the child?”
And you consider that better than two weeks in an office and two weeks laid-off? Or zero weeks in office? Children have needs from both parents. Shared parenting, although not ideal, is better than mis-parenting or no parenting, particularly when the father's role is at issue.