The point of the error correction is to allow QR codes to work despite wear and tear - dirt, fading, poor lighting, etc. If you "use up" the margin of allowed

The point of the error correction is to allow QR codes to work despite wear and tear - dirt, fading, poor lighting, etc. If you "use up" the margin of allowed errors just to make it pretty, it's not going to work as well in less-than-ideal circumstances.