The European Union and NATO have not expelled Hungary because its membership in both organizations is important to the stability of the region. Hungary is a key player in the EU and NATO, and its expulsion would be a major blow to both organizations. Additionally, Hungary is a valuable ally in the fight against terrorism and Russian aggression. While Hungary's government has been accused of eroding democracy and rule of law, it remains an important partner in the EU and NATO.

There are a number of possible explanations. 

First, it is possible that the EU and NATO are reluctant to set a precedent of expelling a member state. If they did so, it is possible that other member states could face similar censure from the European Parliament or expulsion from the EU or NATO. 

Second, the EU and NATO may not want to take action against Hungary because of the country's strategic importance. Hungary is a key transit country for energy supplies from Russia to Western Europe. It is also a member of the Visegrad group of countries, which also includes Poland, the Czech Republic, and Slovakia. The Visegrad group is seen as a bulwark against Russian expansion in Central Europe. 

Third, the EU and NATO may be concerned about the impact of expulsion on the stability of the region. Hungary is located in a volatile region, and its expulsion from the EU or NATO could lead to further instability. 

Fourth, the EU and NATO may be reluctant to take action against Hungary because of the country's importance as a source of migrant labor. Hungary is one of the main transit countries for migrants from the Middle East and Africa to reach Central and Western Europe. 

Finally, it is possible that the EU and NATO are reluctant to take action against Hungary because of the country's close relationship with the United States. Hungary is a key ally of the United States in Central Europe, and the country is seen as a bulwark against Russian expansion in the region. 

Despite the various explanations that have been put forward, the fact remains that the EU and NATO have so far refused to take action against Hungary. The country continues to violate the rule of law and basic democratic values, and it appears that the EU and NATO are content to turn a blind eye to the situation.