Because many "point of sale systems" cost far, far more than $500 and are steaming piles of bad user experience.
But those systems that cost more than $500 take credit, cash, and check. And you get accounting for all of the different types of sales you do. You still need that machine, if you do cash/check sales.
Square lets you record cash purchases, so you don't need the machine: http://d.pr/dGVT
Yes, if you need a much more complicated system then you'll need to pay more, but many people don't. There's no way I could afford, or would want to use, most POS systems out there.
But it's not just taking the cash, but the complete workflow.
But really that's another point that's not so important. My broader point is that this doesn't feel extremely innovative or disruptive. I knew people who did laptop based credit card processing... what 15 years ago? Didn't have the slider, so you had to type the number. And today I can get the equipment for just CC processing for free. And there is some decent software, but the best, like Intuit's is paid.
But this feels really incremental over the course of 15 years. The SW is cheaper, but the transaction percentage is much higher. This doesn't feel like a shift in the way people buy things or companies collect payment in the same way as checks/credit cards/paypal/debit cards did.
Not saying its a bad product, but I'm not seeing the innovation/disruption. I'm seeing a good next step for some use cases.
But those systems that cost more than $500 take credit, cash, and check. And you get accounting for all of the different types of sales you do. You still need that machine, if you do cash/check sales.