It's not totally implausible that the owner is fully aware of the situation and accepts the status quo as a local maximum of profitability, why mess with standing social norms -- much how most restauraunteurs in the states wouldn't dream of paying a living wage for their wait staff because they know customers are going to tip sufficiently regardless of wages and that enough potential employees are fine with the situation (or prefer it) that they won't have staffing issues.
TLDR: It’s remarkable what tipping and basic human decency can do to the quality of service you receive at a bar.
Of course we now need an experiment to disentangle those two variables! One team tips very well, but treats the staff badly , one team treats the staff with plenty of human decency, but doesn't tip. Then we measure the quality of service received by the two groups. I wonder if I can apply for a research grant?
At bars on the other hand the 'corruption' is much clearer. Tip badly for a round of drinks and you'll get slow/bad service for the rest of the evening. Tip well and you'll get priority service and perhaps even free booze. Especially with spirits and mixed drinks the corruption is obvious. Tip well and the bartender will pour you a double while charging you for a single, essentially 'stealing' from his employer and selling you the stolen goods at a discount under the table.