Are you assuming every family member is equally loved, every family member is accorded equal respect, and no family member is vulnerable? That because money is not involved, neither is pressure?
Let's go through some family scenarios then.
Golden Child daughter is not only Too Posh To Push, she doesn't want to 'get fat' with a pregnancy and it will interfere with her busy work schedule. Scapegoat daughter is pressured into carrying and bearing the child. The entire pregnancy is spent with her every movement, everything she eats/drinks being closely monitored and controlled by her Golden Sister, Narcissistic Mother and Enabler Father. She is not included in the post-birth family photograph because the child isn't hers, she's only the aunt. Photo is 'Mother', Doting Grandparents and baby. Her PND from having the child she carried and bore is ignored, she is constantly nagged for being 'a downer' and expected to 'babysit' whilst Golden Child Sister continues to galavant about.
Gay brother persuades childless sister to get pregnant with her own eggs by artificial insemination from his partner, because then he will also have a genetic link to 'his' child. So, not only does she carry and bear the child, she is the actual mother. Brother had promised that she will be a big feature in the child's life, but then there are tensions (sister had not expected to feel this overwhelming protective love) but the paperwork has already been done and legally her child is his. Sibling relationship breaks down and brother/partner/child move several hundred miles away, ostensibly 'for job opportunities'.
Two female cousins, one with a medical condition that prevents her carrying her own child. Other cousin actually volunteers to carry child, having had two successfully and healthy pregnancies herself and really wants her cousin to have her own family. IVF takes place and is implanted into volunteer cousin. There are unexpected complications with this pregnancy and volunteer cousin is left with birth injuries that curtail her own life and mean she has to give up her job, impacting her family financially. Receiving cousin feels guilty and cannot face seeing her now-injured cousin. Wider family breakdown between aunts / uncles / grandparents ensue.
I could come up with more, but I'm sure this gives a flavour of the absolute can of worms such a surrogacy can open. And I haven't even glanced in the direction of how the child will feel about their origins and how they will feel about having been passed from one family member to another like some sort of possession / favour, and how that would affect how they feel about their birth mother, legal mother, the wider family who colluded in it - and most importantly, how they feel about themselves.