Streetwear is a different manufacturing problem from ordinary apparel. A brand does not order one style in fifty thousand pieces; it orders eight to fifteen styles in a few hundred each, mixes knit and woven and outerwear inside the same drop, changes the range every season and needs the whole thing to arrive at once. That is a coordination problem more than a sewing problem, and it is exactly what the Istanbul garment district is built for. Workshops there are small, specialised and clustered close enough that one coordinator can move a range through knitting, washing, printing and finishing without any of it leaving the city.
The second reason is development speed. A streetwear range lives or dies on fit and on the exact hand-feel of a fabric, and both are settled by making things and looking at them. Being able to get a first sample in days, correct it, and see the corrected version the same week is worth more to a small brand than a lower unit price, because most of the money lost in this category is lost on a range that arrives looking wrong, not on a range that cost a little too much per piece.
The third reason is regulatory distance. Since 13 December 2024 the General Product Safety Regulation, (EU) 2023/988, has required that every consumer product sold in the European Union has an economic operator established in the Union who is responsible for it, whose name and contact details appear with the product, and who holds the technical documentation. For a brand outside the EU selling direct to European customers, that is a structural obligation rather than a paperwork detail, and it needs solving before the first drop ships, not after.