A surrogate mother may choose to be a surrogate for altruistic reasons. She may accept money but be genuinely happy to take on the (significant) risks associated with pregnancy and childbirth. That is, of course, something that she is capable of deciding
With the exception of poorer women doing it for money, I've seen some of the women who repeatedly agree to be surrogates for strangers 'purely for altruistic reasons' on TV or read about them and it's noticable that they thrive on the attention they get from the desperate couples, who from the moment the pregnancy becomes viable, lavish them them with 9 months of gratitude, expressions of affection, thanks, love, adoration. Take them on coffee dates, attend baby scans, medical appointments, mother and baby classes with them, constantly express what a wonderful gift they're giving, that can never be replaced, what kind, wonderful, amazing people they are, etc as well as the focus they get from doctors and other health professionals.
It's a huge way to get personal validation and attention. For the few I've seen, once the couple acquire the baby and the love bombing stops...well they want to undergo the whole process again for another couple. In the case where they have their own children they talk less enthusiastically about their own pregnancies.
It's not psychologically healthy behaviour. It's an extreme way of getting personal admiration and validation from a set of people (often professional well off people) who wouldn't normally give you the time of day and 'owe you' for life.
They need counselling and if it were any other physically exacting activity questions would be asked. Giving sex to random strangers for personal validation isn't seen as positive is it? But repeatedly getting pregnant and giving a baby is.
In a way maybe money being exchanged prevents the mentally ill from being exploited. Less likely to get loved bombed when its purely transactional.
I consider choosing to do so for a family member closer to being genuinely altruistically motivated.