Bike chop shops that do that kind of volume do get prosecuted because it’s relatively easy to show that a place is selling a large volume of scrap metal from bikes.
It is much harder to prove that a thief is responsible for 1000 individual bike thefts, because you’d need evidence for each bike.
Proving bike theft is as easy as honeypotting any bike. Its just no prosecuted. It's a cultural blindspot for what I think are probably historical reasons.
You can steal a car priced lower than a bike and get a year in jail. ITs not about the cost of proving anything, it's about the willingness of the institution to enforce it.
It is much harder to prove that a thief is responsible for 1000 individual bike thefts, because you’d need evidence for each bike.