Side or flat sewing one pieces covers is not very common.
We do this process. In most situations the sewing makes the covers more durable. All things considered; the process is expensive. There are literally dozens of different thread colours, textures, and diameters. Most often a client wants edge/side sewing for aesthetic reasons. When one considers the 100’s of cover colours available, and the scores of thread colours ……. the combination of colours can be impressive!