To continue:
ATM's only dispense $20.00 bills in the U.S. If you use an out-of-network ATM you are usually charged a fee, which may, or may not, be waived by your own bank. If one is going to have to go to an ATM at night to secure cash for an appointment with a provider, I do not like the idea of going to a machine, usually outdoors or in a drive-up, to get hundreds of dollars in cash which is a security risk on my part. If you are an un-known (or even a known) customer of a bank and start showing up with hundreds of dollars in cash (tens, twenties, etc.) you may, or may not, be questioned and asked to provide proof of identity (and the bank may, at its discretion turn you into the IRS for cash transactions--even if they are substantially less than $10,000.00 (they may think you are going all over town converting small bills into big ones). You may be able to convert stacks of smaller bills at a large grocery store, where their security measures are less stringent than at a bank, but you also run into the potential problem of the grocery store convenience desk not having enough cash to convert all that you need (if you are a provider).
For me, I would much rather use "Square" (and have done so successfully over the past 18 months or so) and not have to worry about carrying relatively large amounts of cash with the attendant risks and inconvenience. I believe that as we move more and more towards a cashless society, these types of cash transactions, sooner or later, are going to be a thing of the past. Yes, for now, using cash is a relatively anonymous method, but I think that sometime in the not-too-distant future cash may go the way of the check.