What i think its some woman don't want to bond with their babies after birth or dont have the right conditions so the next best option for the baby is being adopted.
So there are lots of options before adoption takes place, adoption is very, very serious and permanent and there can be many reason why a woman doesn't immediately bond with her baby. This is almost never a reason why a baby is adopted. I would really recommend exploring this further if you're genuinely interested but the child is nearly always better off with the mother than with someone else. Reasons why a child might be adopted would be drug use in the home, a violent partner she cannot/will not leave, neglect. There are many others and
just because a woman is poor and may struggle to provide for herself and her baby is not a good enough reason necessarily - I assume this is what you meant by the right conditions? Poor women have babies all the time and they manage.
The lack of an immediate bond, or even if a bond is delayed, is highly unlikely to result in adoption. I would really urge you to consider what a woman would go through in pregnancy, simply not to bond upon sight of her baby and to suddenly rethink the whole idea as - nah, I don't think I want this baby after all.
In addition to the thoughts you may want explore for reasons for adoption may I direct you to Jenna Jamieson's reasons for leaving (and returning to) Porn and Nordic Model Now for some real life stories on the same and also on Prostituition.
For surrogacy you could read blogs by Jennifer Lahl or Stop Surrogacy Now.
There is a lot of information available to you here also, so enjoy reading (and thanks to @SorryAuntLydia for recommending me).