I used to think the same about autos being a waste of electricity but you don't need to have the lights on 24/7.
VinD got me onto DLI (Daily Light Integral) awhile back and it changed my perspective completely.
I've ran autos 12/12 along with some photos and they have still turned out being the best autos pound for pound I've grown compared to autos running on 20/4 or 22/2 timer.
Genetics play a big part but that goes for photos too.
They can be treated like photoperiods and you'll still get a decent yield. Plus you can start them inside late spring and chuck them outside and have smoke before Christmas, or pop seeds outdoors in summer and not need to depend on the shorter days to trigger flowering which is cool.
Have grown an auto in the past, like a photoperiod switching to 12/12 for flower, in a 3.8 litre pot of coco yielded 101g dry and it was treated like shit under weak lighting.
But yeah after that I realized that they weren't as bad when it came to electricity as what I originally thought. Yeah you save 2 weeks veg using photoperiod cuttings but raising seedlings uses bugger all leccy anyways