I would actually be surprised if homeless people remain cashless for much longer, if a substantial number are even cashless now. I am pretty sure even people without permanent addresses can open bank accounts and almost every homeless person in the US has a smartphone. Any homeless people not being directly handed cash or working under the table/doing low-level crime would probably have no reason to use cash. Over time, they probably will not be directly handed cash as much because I don’t think most people will keep carry cash if their only use for it is to give it to beggars.
The other use cases you mentioned are definitely pro-privacy but clearly those blocks are not influential or powerful enough to get governments to allow for private digital transactions. Time will tell but I think it’s really only old people who’d struggle to adapt that are keeping us on cash.
BTW there's a new scam where a homeless person asks for a small donation via EMV but they charge thousands of dollars and then when you chargeback the card issuer asks for your receipt which of course the homeless person didn't give you.
KYC does fuck all to curb crime and mainly used as a tax dragnet and control mechanism for the mostly honest.