If a person is living cash-only, they probably aren't using Uber or a bike share program to begin with.
Again, if a person doesn’t have some sort of credit card, then they can’t use these services to begin with. I think it’s a bit unfair to assume they wouldn’t like to, however.
You don't have to take an Uber or buy things through paypal. You can still go to a store to buy things or take a bus or a train.
The place where I live, like many places in the US, doesn’t have a fully functioning bus system, and definitely no train. Imagine needing to travel several miles to a job interview and you have no car. There’s no bus to take, no bike lanes. Oh, and it’s pissing rain. I’m not making this story up, this was the explanation I got when offering a ride to a guy walking on the side of the road. He said thanks, but that he was almost there.
But we do have ride hailing services here, and they are very beneficial to people who can use them.
What digital currency system would you suggest is absolutely something you can't live without?
I don’t think there’s any digital currency a person absolutely can’t live without. But not having some form of electronic currency in today’s society can be a serious disadvantage, and is one of the many compounding effects of poverty.
My personal opinion in all this, for what little it is worth, is not that business should be required to accept cash. It is that it should be easier to have electronic currency in the first place. Which is a whole other discussion.