I ask because we had a situation in Ireland just like this many years ago. It was for welfare fraud specifically and faced criticism for a few reasons. One was that the suspected levels of fraud may have been much lower than the politician was claiming. The other reason was that the cost of tackling it could likely outweigh any savings.
In the “drug test welfare applicants” it was more about putting extra hassles on poor people than a genuine fraud issue. Voter fraud is similarly an excuse to deny voting rights.