Wine Shelves

If a state law says that a seller is not permitted to go into the store and get their products on shelves or racks and then why they do it anyway? So if they get caught in difficulties obtaining the seller or the store managers?

The CBA prohibits placing vendors, organizing or cleaning products on store shelves that is furnishing the retailer with something of value, which is strictly illegal (California ABC codes from 25500 to 25502).
They do it anyway because it gives them an advantage over the competition, even if it is illegal.
The store and the distributor are liable to get caught.

Monster is just gravy - if a seller does this, it is technically "working" for the store, without pay, for the benefit of the product it sells. It is illegal.