Because this is a dangerous technology which has only proven, again and again, to be unreliable, unethical, inaccurate, and is EASILY used by the people most likely to abuse it.
The point is not that the dutch tax office is corrupt, it is that corrupt individuals and entities are likely, and have used, this for nefarious, foul purposes. Regulating and/or banning its use is only one of many avenues to attempt to safeguard (against) this tech.
