Because of the wrong use of cryptos government won't allow btc simply. But this thinking will change soon. Cause btc has all the legal paper to run their coin in every country.
Different government have different agenda with bitcoin. Some government like japan, Germany, usa work with various bitcoin projects where as some government like china, Bangladesh, Ecuador are against of bitcoin and ban it in their country for their own reasons. According to Chinese government bitcoin affect their country economy by affecting their country own currency value at international market and also affects their bank profits. And in many country it work as a illegal money transaction tool for various anti social work and because of this many government like Israel ban it in their country