Establishment can't control everyone, these are just their attempts at CYA. In a legal sense, they look better for making the effort, and then can attempt to shift the blame to the patron (where it belongs anyways) it all comes down to the efforts of MADD trying to hold bars responsible for alcohol related deaths, thus making personal liability less important because suing individuals does not generally generate as large of a payday compared to suing say a large national restaurant chain with millions of dollars in revenue. The individual is still responsible criminally, but the lawyers go after the business in civil courts for big payouts