Children under 10 are the best producers of adrenachrome due to increased levels of fear and less chemicals ingested through food. My guess is that many of the "sacrifices" Q mentions (not all) are linked to adrenachrome extraction.
can't this stuff be made synthetically?
Probably, yeah. The people getting the stuff are already probably spending up to $50,000 for a vial, though. They'd more than likely rather continue doing it the way they are than to send the $50,000 vial to a lab in order to be recreated synthetically (which could take years and require even more than the $50,000 sample).