Why don't they just adopt? Not that I'm advocating same sex marriage but there are hundreds of children that need homes.
Where are all those children?
Same reason married heterosexual couples keep having children that are genetically their own.
In most states the sex partner of the homosexual may not legally adopt the child. Hether may not have two momies as a matter of law.
You also ignore the overwhelming evidence of psychological problems that are suffered by children raised by homosexuals. There is no normal life being raised by two homosexuals.
Once new zeland study of lesbian women found that the girls were far more likely to be sexually active and bisexual and the boys were likely to be introverted and fearful of other people. (aka shy, agoraphobic)
There is a reason sexual reproduction has proven more valued in nature than this monosexual production theory.
The only reason for this type of attempt at normalcy is to attempt "normalcy" in the PR department. Children are not accessories to a recreational sex partnership.