The main reason is the first one, IMO. If they cordially approved it, it'd probably soften the rest of the problems.
2. Scammers and fraudulent practices: Scammers have found bitcoin as a safe haven cause of its transactions being anonymous. Also, terrorist groups among other sources get funded by bitcoin also cause of its anonymous nature.
There's nothing completely anonymous in the internet. Only levels of anonymity. Even though Bitcoin does provide a decent level of anonymity (if used properly) it's still not used in criminal activity as much as the media say. Studies[1] show that nearly 1% of the total transactions can be linked to anything illicit. There's also no studies which show that the ban of cryptocurrencies reduced criminality.
[1]
https://cryptoforinnovation.org/resources/Analysis_of_Bitcoin_in_Illicit_Finance.pdf (page 4)
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Yes, franky. The reason why it's not worldwide adopted is the block size. Sure, franky.