Because by agreement it can make people more trustworthy in putting their assets in bitcoin and it can make or have a good impact on bitcoin prices and also smoothness in trading or in transactions in the purchase of goods and services.
In my opinion I think bitcoin need approval in every country cause every government want's to protect there people from scam, hackers and bad people using the name of bitcoin in there illegal transactions. If bitcoin got approved in one country many of men there are trust to bitcoin and got to interest to make an investment.
That is right, despite the fact that bitcoin is anonymous in its nature and decentralized still we have to seek for the support from our government since they know best for us and it is for our protection from scammers as well.