The key thing is that the parents should have the right to accept or decline a meeting with the child.
It may be they gave the child up because they didn't want it, or because they weren't able to look after it, or because there were some other social factors at play. It wasn't that long ago that giving birth outside of marriage was considered shameful. It may be that they dearly wanted to keep the child but simply weren't in a position to be able to do so - maybe someone who lost their home when pregnant. It may be they gave the child up and spent the next years regretting their decision but couldn't turn back the clock.
I don't suppose it would do much for the self esteem of someone who spent untold weeks or months tracing their biological parents only to have a door shut in their face, whether metaphorically or literally, because their biological parents want nothing to do with them. I'd also wonder how many biological fathers wouldn't even know that a child exists and how they would react to the news. At least a biological mother would know she had a child and know that she gave it up.