Not to mention that white babies cost premium prices, and black babies come a lot cheaper... (in the US).
My DDs had direct contact and I was happy to support that. They were 13 and 5 when placed (2/3 years after being taken into care for the last time), so first mother was important to DD1 in particular.
Overall, I think it was of benefit (first mum died a few years ago), BUT it was certainly not clear cut. It was very disruptive and contributed to DD1 feeling torn between the familiar, chaotic and fun but dead end life she was born into, and the more structured life of e.g. going to school, doing homework and chores with me. To the point she dropped out of school for a period and had a teen pregnancy and went back into care. If her first mum had lived she may have drifted into that life permanently. Instead, went back to school and is now at Uni.
On the other hand, first mum was happy that her girls were loved and looked after, and so gave them permission to see me as their mother as well. They were never in a position of either of us wanting them to choose between us. That was of benefit to them. Not all first families would do that, though.
DD1's father's family got in touch when she was about 17/18. It was wonderful, they were so welcoming, delighted to be part of her life again... at first. Promised all sorts, then let her down over and over again. I'm glad that she didn't have to deal with that when she was in her younger teens, she had enough painful experiences to deal with. 3/4 years on she is in loose contact with a paternal aunt. They chat now and again, but DD knows that there is no point expecting consistency or support from them.
There is no possibility of contact with DD2's paternal family - the only family member who wants contact was abusive, and DD2 (in her teens) does not want any contact, direct or indirect.
In cases where children are removed for child protection reasons (the majority of cases in UK adoption) contact is far from straightforward. It can add further damage to existing damage, to be balanced against a possible (but not definite) future benefit.