Most materials such as bolts of fabric, rolls of carpet, etc. come in standard widths.  When joined the edges of the material are usually held securely together by tape on the underside or stitching.  Could it be that these "stitching lines" are literally that, edges where some type of fabric or other material has been held together with stitches?  Close examination of various Mars surfaces where "stitching lines" appear shows that some are smooth while others show evidence of some pressure scraping or smudging the surface overlapping each side of the "stitching line."  A sewing machine has a metal foot that holds down the material to be stitched as it approaches the sewing needle.  If the material to be stitched was rubbery, for example, the pressure of such a metal foot might smudge or scrape the surface.  The "stitching lines"  when magnified are not perfectly straight in their interpolation but vary slightly for perhaps one or two stitches at a time, consistent with a seamstress pausing to pull another section of material through the needle area.