They aren't a food source
They have dogshit nutrition. Their body is basically an armored shell and low energy consuming. They exist to hold still, cling to an animal and feed on their blood.
Only during engorgement do they provide nutrition and that is basically the blood inside of them. Animals like tick birds do eat them, but only for the blood they've consumed.
Spread new whacky disease.
Practically all blood feeders spread illness. When your life style involves multiple temporary hosts eventually some microbe is going to mutate to survive in your body and transfer to another animal.
Appear out of nowhere
Ticks lay their eggs near small animals like birds, each meal they grow larger until adulthood.
new whacky color version just appears
Almost all ticks humans encounter are known, what the fuck are you talking about?