Just because something is a delicacy doesn't mean it tastes good. Most people consider a food a delicacy just because its rare, even if it tastes bad. Eating it is only a status symbol.
Most predators don't eat humans when they have a choice, sharks being a good example. We're too bony, stringy and usually not enough fat for their tastes.
For youkai I'd imagine eating livestock to be much more preferable as they're breed to be delicious, they reproduce and mature much quicker and eating food animals instead of people doesn't cause as much trouble for them.
I've got something good for you, Rumia.Y...yeah...It's a little bit rotten, but you can totally eat it!Is it good?What is it?Frankly, I'd rather have pork or beef than human...Y...yeah.Tadaaa! Human meat!
