I didn't want to derail the thread into a surrogacy discussion but anyway, we have diverted that way.
As someone who grew up on a dairy farm I simply see it as farming, using women as breeders to supply babies for those who want them and in most cases can afford to pay for them. A trade in babies.
Some women do claim to love being pregnant and "giving the greatest gift" etc. I simply think they are contributing to the demeaning narrative of women being expected to provide breeding services. Just because it's worked for them doesn't make it a good thing.
Siblings doing it for each other (or other family arrangements) ? Again, no doubt in some cases it goes swimmingly but family relationships are complicated and it can involve a lot of guilting/coercion of the sibling providing the service as well as complications after the baby is born. How many personal accounts have we seen of people who grew up not understanding the family dynamics as the big secret was that their "sister" was in fact their mother and their "mother" was their grandmother. Do we think these modern arrangements are any more pure, and less likely to cause difficulties to the child that was conceived to be given to another family member?
I note none of the Kardashian sisters stepped up to help Kim. Oh no. Because pregnancy and childbirth can wreak havoc on one's body. Best leave that to a woman of lower class/education/economic status who will be subject to a NDA among other contractual clauses.
Women can have serious health problems as a result of childbirth up to and including death. There have been three deaths of surrogate mothers this year alone in the USA, but those are the ones that are known about. Thanks to NDAs most go u recorded unless someone alert notices a gofundme to raise money for the bereaved family. Details are scant.
As @TheMarzipanDildo said, it's not just gay men. It's women, usually in a heterosexual relationship so also het men. And increasingly single men, choosing to avoid the whole messy business of a relationship with a woman whatever their sexuality.
There is also the issue of related exploitation of women who are persuaded to sell their eggs, those sibling arrangements may be altruistic but usually will involve obtaining an egg from another woman.
I'm with @GoodieMoomin
In any civilised society it should never be possible to "commission" a woman to have a baby for you, which she will hand over after it's born. We aren't talking about puppies and kittens here, we're talking about living, breathing human babies. I will never understand why anyone could ever think it's ok to ask a woman to undertake all the physical and emotional risks of pregnancy and child birth simply to hand the baby over to a 3rd party. And what of the baby? Conceived with the aim of being separated from it's mother soon after birth, with all the damage that is known to cause?