You'll get that in some places, sure, but not everywhere. In Norway if people see waiters/bartenders/servers treating other people better, they'll stop going there because the idea is that everyone should be treated equally. And bars are highly regulated - pouring stronger drinks than allowed is a quick way to get your liquor license revoked.
Maybe if it is regulated to such a tight degree; in American bars it's understood there will be "spillage" and bartenders are even encouraged to keep good customers coming back. Generally speaking, if you tip consistently well in most cities in America, and know your bartender, they will make 1 out of 4 drinks free for you or they will otherwise find a way to pour you strong drinks. They know how much they have to spill and they can justify it for a good customer. Only in Las Vegas casinos is this ineffectual, because the liquor bottles are all measured out electronically.
