There are sewing machines that offer didn't stitching modes. In fact, different use cases have different optimal stitches. Like a decorative stitch can be whatever, and a hem doesn't need to handle the same kind of forces as a join, which itself might require different strengths (like a dress shirt sleeve vs a jean's pocket).
Yeah, an obvious approach to stopping it if they really wanted to is to go after those who employ illegal immigrants. You could even incentivize the immigrants themselves by offering protections and such to the point where it's just too risky to hire them unless you're willing to treat them well enough that you might as well just hire someone legally.