Because bartering only works on a small, local level.
Most people wouldn't even be able to barter to get a car ... let alone an apartment or house.
"I need to get an apartment ... I'll trade you 2 weeks of my skill flipping burgers."
"I don't need that."
So the burger flipper would have to find somebody with skills the landlord DOES need, and hope THAT person needed the burger-flipper's skill to barter.
Nope. Using money is FAR simpler than a barter system.
EDIT: Of course, then there's the problem of how do you pay taxes?
This post was edited by Walt O'Reagun at February 15, 2018 10:42 AM MSTMy point was that there are people without skills they can barter for what they want.
Even a genius may not have the skill set a landlord needs, in exchange for a place to live.
Then those people would have to find a 3rd party with barter the landlord wants ... and try to barter their own skills to that 3rd person.
EG: I have eggs to barter ... the landlord wants butter ... I have to find someone with butter, who wants my eggs. Maybe the person with butter doesn't want eggs, but wants lumber. Now I have to find someone with lumber who wants eggs, so I can give the lumber to the person with butter, so I can get the apartment. And what if the person with butter leaves the area? Or the landlord doesn't need butter the next month? Now I have to start all over again.
I still say cash transactions are much simpler.
NOTE: If someone ever invents a replicator ... like in StarTrek or The Orville ... it will immediately render the need for money or barter worthless.
Sure, we all have multiple skills ... but I used one for the simple reason that there are times when none of your skills are going to be wanted by the person you're wanting something from.
There has been currency since before written history.
Which tells me that people thought money was necessary even before they thought written language was necessary.