This is my cat, Max. His dad was a feral maine coon and his mum was a lazy barn cat. He is simultaneously weirdly crafty and the most head-empty animal you could meet.
He yaps a lot which is normal, he likes annoying the birds at our window. But also he will not stop eating hair? I don't exactly leave random strands of hair everywhere; my wife and I have shoulder length & extremely long hair respectively, but we always put stray strands in the bin.
Idk where he even finds it, but he eats hair. He loves to eat hair. He sits by the couch or our carpeted stairs and he chomps at the air, trying to grab a spare strand and eat it. He chomps like mad all day at random places. Occasionally I catch him dragging his ass, because he has a turd hanging from his butthole by a long strand of hair 
Why on earth does he do this? How do I stop him? Why is my dog so dumb??
Do they do it for fibre/aid digestion? If it helps clump the poo up (despite the long strands). Plus they ingest so much hair from self grooming anyway what's a little more gunna do
Well small hairs are fine, hairball, but I worry about the strands in his intestines and stuff, y'know. Can cats get fibre from hair...?
Also Idk, my boy has always been a healthy, solid pooper. He does puke more as a result of this it seems
I guess because hair (made form keratin, a protein) doesn't break down in the gut, it could serve a similar digestive function to the plant fibres humans and other animals get through their diet. So not really fibre by the same chemical composition but fibre in the sense of 'long resilient threads'
The dog has an instinct to eat my fucking hair
Uh is there something I can substitute that's less annoying and has lower chances of dangly turds?
Not sure, I've only ever kept dogs and we just kinda put up with their weird habits, like, eating grass to puke. When I've looked after friends' cats before they say not to worry too much about the hair. They use static or sticky rollers to clean their own hair from clothes and furniture as best as possible.
Hopefully some long-hair cat carers can chime in with better advice.
I mean if it's not a risk it's fine I suppose, the dangly turds are annoying but only that, so...
Cleaning a nerds rope from the litter tray is always fun, hey