Seeing that you have experience in this sector, what is the purpose of a bar exactly? I never have gone to a bar, but always have had the assumption that bars are pretty much for getting plastered.
For 30$, you can make yourself enough very nice booze, flavoured to your tastes, as you would be able to get for $300 or so at a bar.
As for the direct question: different bars have different purposes, which is why there are so many different types.
Bars in the financial district are often vehicles to waste money as a social display. Bars in the artistic sector are often vehicles to meet likeminded poor, but cool, artists and misfits. Bars in residential areas are normally places to relax and have a few pints. Bars in the nightlife areas are normally places to meet people. Some bars have good food. Some bars have cheap drinks. Some bars have great music. Some bars have familiar staff.
There's a bar near where I used to live that offers manicures, male model servers and foot rubs. A few streets down is a sports bar which seems to employ exceptionally chesty waitresses. As you might imagine, the target demographic for each is different.
They might actually be the least efficient retail or service venue for achieving that purpose.