their is always criminality everywhere even in bitcoin, bitcoin can be used in good terms and also in bad terms because it is anonymous, you can use it in illegal transactions and etc, I think that is also the reason why most of the government around the world is refusing in the bitcoin to be an official currency in their country. But I think the problem is not on bitcoin but on its regularization.
The problem when you invent something is that you never know how people are actually going to use it. Are they going to use it for good or bad or are they going to use it for a much different purpose?
With the reason that bitcoin isn't the official currency of a country because bitcoin is being used by criminals for illegal transactions, then every single fiat should already be burned by now. Bitcoin is known for being used in the deep web but fiat currency are certainly used 1000x more frequently than bitcoin for illegal transactions. With all the corrupt government, all the huge syndicates, and all the drug lords out there, with no question, the amount of fiat being transacted for illegal stuffs exceeds the market cap of bitcoin. Just think about the amount of bitcoin users (around 0.00x percent) and the amount of fiat users. It's all statistical.
I think the reason the governments are not accepting bitcoin is that it exploits the idea of having a non-taxable money and the idea that fiat currency is constantly inflating.
The bitcoins are helping the police because now a days millions of people use bitcoins instead of keeping cash with their self thats why the thieves are not able to snatch bitcoins because it is the most safest way to keep your money in there fore police should be thankful to Bitcoins.