system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do middlemen exist?

If we, as consumers, can buy directly from the source, why would we pay the markup that a middleman charges? I think this is more relevant today because people can easily sell their merchandise directly by opening up a store online, instead of going through a retailer like Amazon.
gpt
Because running a store takes a lot of work and effort.  

Some suppliers do this, but many don't.  In a nutshell, they would have to start shouldering responsibilities like inventory management, website management, store front management, shipping orders, customer service (to a larger degree), etc.  

By selling to a middleman to resell, they can avoid the hassles that come with selling direct to customers.