I'm not saying that they will work. But acupuncture and yoga are not the same as pixie dust, dung pills or what have you.
To give an example of what I mean: the waters of the Ganges were said to have "magical powers that cured disease"[0]. It was later found that the waters contained bacteriophages that killed bacteria. Could anyone have guessed this?
Okay, so why don't they show any efficacy above pixie dust in double-blinded studies?
It's all deeply frustrating. I tried acupuncture a few years ago (at a doctor's recommendation) and did a lot of reading. It didn't work for me, unsurprisingly - about the only thing it's been shown to have any effect for is some types of lower back pain, and my pain was (is) mostly in my hands.
It doesn't seem completely impossible. You could have someone put the same needles in randomly, instead of in whatever location acupuncture claims they should be put in.
Therefore single-blind studies of acupuncture are trivial; just find people who don't know where the needles are supposed to go. A double-blind study could be possible, if you trained two sets of people to perform the procedure (one incorrectly).
This study introduces them and shows that acupuncturists can't well distinguish both types: https://www.biomedcentral.com/1472-6882/7/31
This study uses them to check for differences in pain-relief (there are no differences): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2765771/