I think that mending clothing and other textiles has got to be the greenest use of my sewing machine. It's extends the life of clothing that we already have, thereby preventing the need to buy new or even used clothing.
But... I just wish mending were more fun. It's really kind of boring.
I vastly prefer to make new things, be it napkins, clothing, or matching couch pillows. Sometimes when a mending job is challenging, where I have to think through just how to repair the item - that makes it a little more interesting.
Ah well, before I sound too doomy and gloomy - I have to brag that by repairing my husband's jeans, that I've saved the household literally hundreds of dollars at this point, and in fact, the savings has been great enough that it virtually paid for my sewing machine. So, there are indeed rewards, just not interesting ones. ;-)