Because the custody battle would go something like this:
The Husband: You can have the kids....
Me: No, you take them!
TH: That's very nice of you, but no: they're all yours!
Me: Really, I can visit them!
TH: You can have full custody!
Me: You take them!
TH: No, you!
PS. to my darling sons who might read this when they are all grown up: please know I am totally kidding (sort of).