Also surprised it hasn't been feudalised somehow. Some company owning all the machines and then uber-ing out the hard work of siting them and restocking them. Gamifying the process of monitoring, "your fleet", the "ching" on your phone when someone buys a bottle of water or candy bar. Special deals for site owners. Branded supplies. An app for customers to talk to the vending machine. Loyalty points. A snack radar. Etc.
I think it's great the market is mostly independent operators.