VISA inc. 及八達通到底是做甚麼生意?

Visa business = Credit services.
You dont need to put money in first.
Give a personal credit amount to you, increase your liquidity.
Earn profit by their services.

Octopus Card = Did not provide Credit line to you.
You need to put money in first.
You dont need to bring the coins and money along.
Earn profit from their services charge

They are both target to provide a kind of convience services to consumers,
so that its easier for a person, like you and me, to consume.

Retail shops are happy to cooperate with them, because, VISA and OCTOPUS
services let customer spend money more easy. A consumer dont need to worry
about carry a big sum of money running on the street, and VISA help them
that even they dont have money today, they still can consume.

Actually, VISA and Octopus is providing a money supply services in between the Consumer and the Retail Shop that the retail shop alone cannot provide.