This is still a question nowadays because not all country gives a go signal for bitcoin. They are taking a lot of things just to slow down the growth of this currency. If not eliminate the whole system. What can you say guys.
Bitcoin is not at all a threat to the economy but it is indeed good. Let me explain why. 1. Bitcoin increases the purchasing power of common people/crypto investors. So if a person earns more, they will spend more for good and services. It will increase the indirect tax income for the government. because the majority of a government's income comes from indirect taxes and not from the direct taxes like income tax. Every product you purchase, government get the tax. So if common people starts spending more, it means good for the economy of that country.
2. Bitcoin or crypto currency market helps people with alternate employment. I personally know a lot of person who are fresh out of collage and earning well from the crypto currency market by investing, trading or providing services. These particular group of people are the new age people who are comfortable with computer and programming. They have found an alternate employment through crypto market. In majority of the countries, where the governments have failed to provide jobs to the eligible youth, a place for alternate employment is a good news.
3. Crypto can't be mainstream because of its de-centralized nature. So every time anyone wants to use their crypto income, they will have to exchange it to their local currency. That helps the money circulation among the citizens and directly supplement the point no. 1.
But bitcoin or cryptos are generally a threat to the banking business unless the banks are going to adopt it. Again, let me explain why, 1. The current market cap of crypto is close to 450 billion USD. This is the dollar value equivalent which has been converted in to crypto worldwide and this is a very serious amount of money. If crypto didn't exist, this amount of money would have flown in to banking channel. But that has not happened because crypto exists and people are investing in crypto instead of investing in to bank deposits. So it is a threat to their business.
2. Governments and banks are in direct control of your fiat funds. If you do anything out of the line, banks can simply freeze your funds and ask for an explanation. With crypto it is not possible. Here you are the controller of your own funds. In today's world, money means power. The more money you have, the more powerful you are considered. You can do whatever you want with your crypto funds which is particularly the reason why governments are still unsure about cryptos. Money laundering and terrorism funding are two very serious reason behind that. Due to the pseudo-anonymous nature of the crypto transactions, it is very hard to detect such crime. As a good citizen, I am sure you won't support terrorism funding in any way. So it is a thread to the governments as well.
There are more reasons for the argument. But I believe I have covered the basics here.