From A History of Iran: Empire of the Mind, by Michael Axworthy (Basic Books, 2016), Kindle Loc. 3561-82:
Traditional tribal costumes vary enormously across Iran even today, and are often colorful and eye-catching, with no veil in sight.
Of the remainder of the population, the majority were peasant farmers and laborers. But among these people, too, women had an essential economic role and some independence (insofar as anyone in the poorer classes could properly be thought of as independent). Women had to work hard in the fields and probably did the majority of the routine work—of all but the heaviest sort. Again, a veil of the enveloping chador kind was normally quite incompatible with that sort of activity.
Even in the towns and cities, the majority of people were relatively poor, and in those households most women would have had to work outside the home. And there were significant numbers of prostitutes, to whom the rules of respectability certainly did not apply. So the setup we might think of as typical—of heavily veiled women seldom leaving the home and even in the home kept apart from males who were not relatives—was in fact atypical before 1900. When it did occur, it was limited to middle-or high-class families in towns (precisely the class that looms large historically, being the book-writing, book-reading class—perhaps only four percent or less of families overall). But that arrangement was, or became, an aspiration for many men who could not afford to make it a reality. One could think of the heavy veil as a kind of elite fetish, similar to some of the fashions of nineteenth-century Europe that immobilized women, being wholly impractical and incompatible with work of any kind. For a man’s wife to be out of the house and out of his control, especially in the towns, perhaps partly because of the presence of prostitutes in the towns, potentially exposed him to derision and ridicule. But for her to be kept at home and to emerge only veiled was expensive and a sign of the man’s status. It would be easy to overlook or underestimate the significance and implications of this trope among men in Iranian society and elsewhere. Rather than being an outgrowth of traditional religion and society—there is little justification for it in the Qor’an or the earliest hadith, which originated in different social circumstances—it may largely underpin them. Possession of material goods had its patterns and its social consequences, but so also did the possession of women.
As the population later became steadily more urban and in some ways at least more prosperous, more women were more restricted, stayed in the home more, and wore the heavy veil. But we should not think of those arrangements as typical of pre-industrial Iran; one could accurately say that for the majority of Iranian women, they were a twentieth-century innovation.
An interesting comparison with foot-binding in China.