Wa alaikumus salaam
Non Muslims have always had some very distinctive dressing and appearance traits. A Hindu wears a Sari and sports a red dot on the forehead. A Buddhist would Don his orange garb and his head will be shaven, a jew will wear the small hat (yemukah) or a type of wide brimmed hat with platted hair and a christian a white habit. Many more examples can be given. Western fashion would include a shaven beard , nude clothing, high heeled shoes and a variety of enticing perfumes. The Persians in the time of Rasulullah ﷺ shaved their beard and lengthened the moustache and the pagans wore a turban, but without a headgear and using hair oil. They also did not use kuhl or antimony. We were told to oppose them and lengthen the beard and shorten the moustache and also to wear a turban with headgear. Many more examples can be given . The point is that our dressing should set us apart from the non Muslims and should be a type of advertisement for Islam .
Regarding the long thaub worn by most Arabs nowadays , it's more a cultural dress than an Islamic one. The real sunnah thaub reached only halfway to the shin and had a slit on the side. However in western contries it has become a symbol of Islam, so many wear it due to this reason .
And Allâh Ta’ala knows best
