Well because some opposed to it. They cant control it since bitcoin is a full decentralized. Ofcourse some from the Govt wanted it taxed but some users hate to be under surveillance too from them and thats what Satoshi goal not to be underwhelmed by the Politicians. He makes bitcoin for everyone and no one should take advantage of it.
Bitcoin network is decentralized and can not controlled, manipulated by any single person, mining pool, miner, government so it is very strongly unaffected by governments globally. Governments as we know in long history of human civilization have never been agreed with each other in any issue so it's unrealistic to ask all governments globally agree to make Bitcoin legal in their nations and over the world.
The good news is Bitcoin Legality Map has turned greener over years.
https://newhedge.io/terminal/bitcoin/legality-map