Creating a DNA database of criminals is a time consuming task and the budget allocated towards that task might find a better use in multiple of other places. Criminals are humans who at one point of their lives commit a crime against the state, people and/or humanity. However people do change and entering a database of criminals almost marks you for life. Instead of building that kind of database, it would be easier to build a center for education of the criminals inside our Government.
A creation of a DNA database would not be a major budgetary burden as it would be possible to create the database using already collected DNA. The majority of the expense would have already been spent leaving a relatively small amount to be spent on developing the program to be used across all platforms and training to use the database effectively. Any money spent would be an investment in prevention of future crimes by habitual offenders.