Considering how much time you spend in bars, I'm surprised you find that interesting. It's SOP in lots of bars. I did it tending bar 30 years ago. Pour cost is everything and bartenders are under the gun to keep pour costs down. They have additional incentive to keep it down so they can push the occasional drink to good, regular customers.
Some houses are so bad that they'll put well liquor into high end bottles, but in my experience most don't do that. Too easy to get caught. What they DO do, and often, is use well booze in place of call liquors in mixed drinks, especially sweet ones. If you order a call drink; Jack and Coke, Grey Goose or Hendrick's and tonic, etc. and aren't sitting at the bar watching the bartender make it, there's a high likelihood you're getting well liquor. I kept my pour costs in line almost exclusively with strawberry daquiries and ice cream blended drinks. On the theory that people who order those don't really want to drink, I left the booze out entirely. Never once did anyone complain.
Bottom line: you're getting hammered and trying to get lucky while the people behind the bar are finding new and better ways to empty your pockets and fill theirs.
Cheers!

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