The UK government only did this because of a ruling by the European Court of Human Rights, in the S v Marper case, which said their policy of taking the DNA of anyone arrested for an offence was indiscriminate and not proportional. Before this ruling, the UK Government could take, and keep, your DNA profile if you were arrested for a motoring offence, and later acquitted. Or if you were taken into custody for being drunk on the street. Or if you gave a witness statement to the police. Basically, if you came into contact with the police, you'd get your DNA stored permanently.
What it led to was ridiculous situations: Kids under the age of 10 being on the Database. One third of the black males in the UK being on the Database, Half of black males in London being on the database. The corresponding figures was whites, by the way, was around 15%. Not only that, but DNA is only successful in 0.37% of all cases that come before the police.
Finally, adding DNA profiles of individuals onto a database doesn't lead to more detections if the rate of Scene of Crimes profiles added to the database isn't proportional to the individual profiles. The rate of detection of crimes using DNA didn't go up between 2005-2007 eventhough the number of individual profiles on the database went up by around 400,000.
Finally, the Home Office approved the use of the DNA Database for research purposes, without publicising any information: neither the company doing the research, nor the topic of the research. That's a bit fucked-up.
DNA can be useful, but only in specific circumstances, and only for certain kinds of crime. An ever-growing database like the UK had, was not only super expensive, it was also pretty useless. It's aim was not really to fight crime, it was to fight the fear of crime. Just like pretty much every single policy from this government has been about fighting the fear of crime. Not crime itself. But people's perceptions of crime.
Thank fuck for the ECHR.