Why don’t people dress in their native clothing anymore?

Thousands and Hundreds of years ago each nation had their own unique style, but now all nations(specifically the majority of its people)dress in T-shirts or jeans and traditional clothing is usually only used for occasions now or reenactments, why is that? I’m not against modern clothing or anything I just don’t understand why each nation wears the same thing now, back then clothing used to be a lot more stylish too, look at the Chinese Hanfu, Japanese kimono, and Celtic outfits for an example, so what’s the blame for why everyone dresses the same now?