Somebody who wants to be a "real" bartender should have a well-versed knowledge. Not only about drinks (this is pretty much the beginning), but also what just happens in this world: politics (even though, you should not bring it into a bar), sports (same as before) and culture - not only music (and I don't necessarily talk about pop culture), but also classical music, jazz (...), literature, visual arts... but also science... basically everything what happens on this planet.
You don't necessary need to be an encyclopedia and you can have "dark spots", but you should have definitely heard of the Higgs-Boson particle or Jeff Koons.
In fact, a lot of classic bars were directly connected with arts - not only that artists (like writers, but also any other kind of creatives) were frequenting them regularly - but there were also references to art: In Harry's Bar in Venice, Cipriani named a drink and a dish after famous Italian painters: Bellini (paintings of Giovanni Bellini) and Carpaccio (paintings of Vittore Carpaccio).!
I feel nowadays we fall short of understanding arts or referencing it. Which bartender takes note of the previous points - maybe talks about this with his guests - or just calls a drink after these references.
Why is there no "Planet 9 cocktail"? In a time, where knowledge is just a "google" away, it seems, that we loose ourselves in reality shows and "Lady Gaga tunes".