since BTC is something relatiively new and by this I mean that not ever before have so many people around the globe been intrested in it and start using cryptocoins,many countries do not know how to manage it in a legal and financial way. Many maybe consider it a good way for money laundry and want to block such actions. Others have no clue of the thing and do not want it to take control of the market before the govs become experts themselves. An other reason may be...the Banks. With BTC you have no need of the banks, unless you have a good amount of btc and want to cash out, but, ig btc is the future as many hope and believe, the way it works leaves the banks in the outside, only fees in exchanges on the internet are gaining. So the banking system as it is now, would really hate if all the transactions are made in btc cause money loses all its value and so do banks.