When talking about ethnographic groups in the Balkans, it is important to understand that they often represent regional cultural communities within a broader nation rather than isolated or ancient populations. These groups could have distinctive customs, dialects, traditions, and traditional costumes, yet they share many elements with the wider national culture they belong to.
People who moved into a village, town, or region (whether from another area or ethn. group, another part of the country, or even different ethnicity) were often expected to adopt local traditional costumes and customs. Women who married into a community, as well as entire families who settled there, were required to abandon their previous regional traditions and immediately adopt new local ones. Those who did not would face social exclusion, ridicule, or being viewed as outsiders. In many communities, proper dress was tied to social respectability and belonging.
Result of this was cultural assimilation, over time, people of different origins often came to share the same customs and even identical traditional costumes. In some cases, the population preserving a particular regional culture was not descended from the area’s earlier inhabitants at all, rather, they had adopted the local traditions after the previous population (whether of the same ethnicity or another) was assimilated into the new majority, migrated away or died out. This of course doesnt reffer to the nomad communities, such as Sarakatsani.
This is one reason why traditional costumes should not be treated as definitive evidence of ancient population continuity or used to construct theories about a people having inhabited a region for thousands of years. Older population does have an influence on the culture of the new population, but very often community is consisted of newcomers, rather than people who live there for thousands of years. Traditional costume is shaped by available materials, climate, geography, local crafts, and occupation of the population, whether they were herding, farming, doing crafts or trading. When settlers move to the new region, they start using the resources and materials that are available. Ethnographic groups could be a relatively new or very old group, it really depends.