I'm lucky to be able to say that I haven't experienced it directly to be able to answer in more detail but the article I linked suggests that it is a bit of bot

I'm lucky to be able to say that I haven't experienced it directly to be able to answer in more detail but the article I linked suggests that it is a bit of both. Some senior police officers interpret the rules in a way that suits them, some people say the law as written is ambiguous. I mostly interpret "Unable" in this context to mean it would require too many man-hours to clean up the database because it has been allowed to grow too large and disorganised. I can't back that up with evidence, it's just something I recall hearing. There are no doubt other reasons and this applies to the overall picture rather than individual requests for removal. In the case of an individual request I could still imagine that the system is so badly designed that it isn't actually possible to locate all parts of a sample, all references to an individual in the (various) database(s). I've seen environments like that in the corporate world, I assume the government is capable of creating them as well.