Transactions solely transacted via physical cash don't require a middleman be paid at every step. Even if you never see a line item for the middle man its effectively part of the bill you pay when you check out anywhere that accepts plastic.

The middlemen by setting costs that include a minimum charge per transaction also make transactions below a certain threshold non viable because the transaction fee would be higher than the actual charge.

Cash comes with costs too, often paid to middlemen. Large businesses need vaults, secured trucks, extra time wasted counting and verifying it, etc. Even small business will often need extra insurance, plus the risk of getting their employees harmed on the way to the bank.

Ask all those marijuana shops trying to get bank accounts if they don't have any costs passed on to the customer for dealing with cash.

Physical cash is a primitive technology so its use cases are quite limited given the superiority of alternatives.

Electronic cash in the form of cryptocurrency can make money transfer much cheaper than it otherwise would be. It also doesn't require you to jeopardize your privacy every time you form a financial relationship with a new company, as happens every time you use a credit card with a new company. In fact, your privacy is at risk every time you use an identity linked payment system, given the possibility of hacks/leaks.