জামদানির উল্টো পিঠ খসখসে কেন?

Because it is hand-woven. Each motif thread is inserted separately and then cut or tucked at the edge of the figure, so the reverse side is covered in small, slightly uneven thread ends. That roughness is the signature of the craft, not a fault.

A power-loom copy or a printed Jamdani has a smooth, even back — which is exactly how you tell them apart. On a very fine piece the ends are short and neat; on an everyday piece they are longer and more visible, and both are right.

Do not trim them. Cutting the ends flush weakens the motif and can start a pull. Wear the saree as it is; the back is never seen.