Artemis3, Bittrex does not make such a move just like that, but because it has to comply with laws and regulations in USA&EU. They know that reducing the number of users means less revenue, but they have no choice, or they will do what they are just doing, or they will be stopped from doing business.
I will just quote part of their TOS :
Restricted Locations
You may not use the Services if you are located in, or a citizen or resident of the United States. You may not use the Services if you are located in, or a citizen or resident of any state, country, territory or other jurisdiction that is embargoed by the United States, or if you are on any trade or economic sanctions lists, such as the United Nations Security Council Sanctions List, or if you are restricted or prohibited from engaging in any type of trading by the European Union, Hong Kong Monetary Authority, Hong Kong Customs and Excise Department, Office of Foreign Asset Control or any other administrative law enforcement agencies. You may not use the Services if you are located in, or a citizen or resident of any state, country, territory or other jurisdiction where your use of the Services would be illegal or otherwise violate any applicable law. You represent and warrant that you are not a citizen or resident of any such jurisdiction and that you will not use any Services while located in any such jurisdiction, and that you are not on any trade or economic sanctions list. You also may not use the Services if you are located in, or a citizen or resident of, any other jurisdiction where Bittrex has determined, at its discretion, to prohibit use of the Services. Bittrex may implement controls to restrict access to the Services from any jurisdiction prohibited pursuant to this Section 2.2. You will comply with this Section 2.2, even if Bittrex’s methods to prevent use of the Services are not effective or can be bypassed.
I'm surprised Ethiopia is in the list. This country is trying hard to get better. And its leader just received a Nobel prize!
Maybe the Nobel Prize is the reason, Trump is jealous because he didn't get it, so he put Ethiopia on the list