I used to get sent the magazine 'advertising' children for adoption. We were members of adoption UK because our LA paid for our membership (because we were kinship adopters).
Many, many of the children in the magazine had outrageous names. I will never forget little 'Rave' for example.
But lots of them also had names like Maureen, Callum, Jake, Sasha etc.
It could be that if you have a particular dislike for the unusual names you are more likely to notice them as they come through the courts/their files land on your desk?
We tend to notice things that back our theories up dont we? Its natural. I am far more likely to notice a story about a horrible Tory MP for example 
My birth children have semi unusual names in that they are quite 'cool'. My adopted son has a 'chavvy' name. Its not even spelt properly. It does worry me that he will be labelled because of a name given to him by his birth mother (who you are right, did far worse than give him an usual name) who he never sees and has no influence over his upbringing.
I can see that you are more angry about the implications than judgemental about the children involved and I can understand that. I do get that the kids you are working with could do without the extra 'burden' of a made up/misspelt name.
I do think the problem is with societal attitudes. But I think this has always been the case though. If you were called Daisy or Maud at a certain time in history that would have marked you out as a kitchen maid.