Several reasons. Perhaps they couldn't supply an army or force to fight, perhaps they acted only as economic powers rather than military powers, or there is also the possibility that their governments felt they had nothing to gain and was not worth fighting.
Countries in Europe that were Neutral in World War I:NorwaySwedenDenmarkNetherlandsSwitzerlandSpain
belgium, poland, and all those countries in between
Many countries were neutral during World War I, like Switzerland.
They are called neutral nations. These countries were neutral during World War 2: Spain, Norway, Portugal, Ireland, and Switzerland.
ya mum
Switzerland, Turkey, Portugal, Sweden, and Spain were neutral countries in World War 2.
I only know one which is Brazil
2 countries, Switzerland, Netherlands
There were some countries that were neutral during World War 2 that invaded Germany. These countries included the United States and Sweden.
They wanted to stay neutral-out of the war
South Africa
Switzerland and Sweden