The worst bid’ah with regards to clothing is that of the Rafidah (and some Sufis) who have institutionalised the hideous bid’ah of clerical attire that is literally designated for a specific class of society i.e. the clergy.
This is an ugly bid’ah taken from other polytheists (Church, etc.) and started during the Safavid take-over of Persia (when modern-day Iran was forced from a majority Sunni country into a majority Rafidi Shia one) and is ever since an essential part of their religious institutions (‘scientific seminaries/al-Hawzat al-‘Ilmiyyah’) and those who graduate from them (or are given the ‘blessing’ of wearing the Rafidi turban by one of their scholars).
Iranian Shiites are more secularised than Turks and by large irreligious. That’s known. On top of that traditional attire is rarely worn in their circles, instead, they are known to dress like most Western people (which is ironic, for the Shia sellouts in Iran claim to oppose the West and Iranian nationalists boast with their Persian heritage, yet both walk around like an average Joe in the States with a shirt and trousers).
South Asia was directly colonised for centuries, yet people (including Hindus!) retained their attire.
Shia Iran – which wasn’t colonised – willfully abandoned traditional garb with the exception of the clergy who exploit their clerical attire and have literally started a form of priesthood in Iran (a respectful form of addressing the Shia clergy, a form which they themselves prefer is rouhani/رحاني in Iranian Persian which literally can be translated as ‘priest’!).
In comparison, Iranian Sunnis, are way more religious and conservative and unsurprisingly traditional attire is very common in Sunni regions of Iran like in the south of the country (Fars/Hormozgan) and the Iranian Khorasan province(s) which are home to ethnic Persian Sunnis.
On top of the bid’ah of introducing clerical garb to the religion, the Shia clergy also propagate the nonsense of designating the colour black (and thus black turbans) to the ‘descendants’ of the Prophet (ﷺ) so-called ‘Sayeds/Syeds’ and white for people with non-royal blood (so to speak). A bid’ah unknown to Islam, the Prophet (ﷺ), his Ahlul-Bayt and Sahaba wore turbans in various colours.
The Rafidi argument that certain people in society wear specific attire (firemen, police, etc.) is flawed because the attire of some members (rather professionals) in society exists due to necessity (like the Police that must be visible). If the attire of the learned scholars and students of Islam was of utmost importance, then the Prophet (ﷺ) himself would have started to dress significantly different to the people of his time, yet the truth is, the did none of that (i.e. the dressed just like his people minus prohibited elements of their attire).
Al-Hamdulillah, the Sunni world by large (except some institution like Azhar that was founded by Isma’ili Rafidis), have not fallen into this bid’ah, thus you will find the Imam of a Mauretanian, Sudani, Afghan, etc. masjid dressing just like the people behind him, same in Arabia.
PS: Some Shia clerics argue that certain people in society wear specific attire (firemen, police, etc.) and thus the Rafidi Rabbi/Priest attire is justified is flawed because the attire of some members (rather professionals) in society exists due to necessity (like the Police that must be visible). If the attire of the learned scholars and students of Islam was of utmost importance, then the Prophet (ﷺ) himself would have started to dress significantly different to the people of his time, yet the truth is, he did none of that, instead he dressed just like his people minus prohibited elements of their attire just like most Muslims in the Muslim world, from Mauretania, Sudan, Arabia to Indonesia and even in the Sunni regions of Iran.
All Iranian Baloch and Persian Khorasani Sunnis (Mashad still has a Persian Sunni minority, towns outside of Mashad like Taybad, Torbat Jam, etc. are even majority Sunni) wear the Shalwar Qamis, like many other people in central Asia. The Persian Shia are the only ones in Iran void of any religious/traditional attire, even the Persian Shia of Khorasan in Iran.