Many women are coerced into doing it by their fathers or husbands, who then take the money. There are women with learning disabilities who are signing up not understanding what they are doing - they may think they will get to see the child for example.
People often think surrogacy for a family member is ok but family can be the worst for coercion - especially of its young women. Sisters may look happy to provide a baby for a sister or gay brother, but how much of that was due to family pressure?
Then the impact on the baby - removed at birth, never seeing birth mum again. Often a separate egg donor has been used, who they will never know either. In the UK you can get info on donor and surrogate at 18, but if your surrogacy was done overseas, chances are you will never know.
We don't remove babies at birth in adoption in the UK because we understand the impact on the baby - but this is ignored in surrogacy. These surrogate born children will probably not be allowed any space to grieve their losses or work out identity issues - like children adopted in the olden days they will be expected to accept it/be grateful.
And then there is the lack of checks on purchasers. Single men are buying babies, no questions asked.
Purchasing fathers are usually the biological father so are entitled to be the parent in most cases. Since the alternative would be taking the child into care, most purchasers do get what they want.
There have been cases in the UK of people in their 70s having babies by surrogate. In one case the "mother" had a stroke and was in a care home, then she died, but the child called her "mum" and was taken to visit her. Are elderly people having children to look after them?
Purchasers change their minds and abandon unwanted babies or get the surrogate to abort. They put outrageous demands on the surrogates, like no pain relief in labour or complicated dietary rules, which they themselves would never tolerate.
And so on...I could write a book on this!