They have publicly accessible computers at the public library and you can get a prepaid CC. It's more difficult for those without these things in their home, but not impossible.
It's the nature of the world we find ourselves in.
It's one of those old Spock adages
"The needs of the many outweigh the needs of the few"
More difficult? Sure, but not impossible.
It shouldn't be that difficult. I can't imagine what would happen if you required a CC, email, and PIN to vote. I don't even need those items for auto registration. The bottom line is that these processes make a purchase more difficult. Could you pay with cash and use the dealers credit card? Can you have the software create an email account for you at the dealer? Can the PIN be mailed to you, like credit card PINS are mailed?
How many times have we heard that the government (i.e. IRS) does not do business over the internet. I cannot submit my heath insurance claims through the web, or fax them forms. Strictly by mail only. (BCBS)
What's going to happen when you need to pay with BitCoin or Paypal. It seems the General Assembly could have required payments in that form without challenge either. What if confirmations to all this were required to be via instagram, now requiring a phone.
My bottom line is that no matter how many requirements they impose, you should still have the option do anything with cash, and the USPO.
Final note (edit): When I have gone to the public library to study or use the net, I am sometimes asked to show my library card. When at an out of town library, getting one is a hassle. Also, there are never enough computers, and there is a time limit. A password and username is sometimes required, that is generated through your library card. So, your activity can still be tracked. So, for a one time use of the public library, it is a PITA as well.
Edit 1: So now you need three trips to the dealer. The additional trip is for the dealer to give you a list of requirements prior to purchase. Almost like a NFA items. Go to the post office and get pictures taken (i.e. go to the library and get an email and pin).