Fine, let’s talk post paid. Electric bills. How you would you feel about an electric company that sent you an invoice and wanted to be paid daily? Yes, yes, the analogy is also imperfect because consumer electric companies can do auto-pay and walmart generally does not for small vendors. But please try to see the point even with a less than totally perfect analogy to consumer life.
This would be trivial via Direct Debit.
I know that in Australia the terms in groceries are horrendous. Generally, frood vege suppliers have to buy specific boxes for delivery (from the supermarket chain) they then still have to pay rent on those boxes and if items don't sell they have to take them back (and pay a box use fee again), make items available at discount for specials run by the supermarket, on top of that the payment terms are as described above. Essentially the big chains don't take any risk, and the small suppliers all the risk. This might be particularly bad because the market is dominated by 2 chains. Supposedly Aldi and Lidl were much better at the time, because they tried to break into the market.
This situations where paying in advanced _every_ time would be cumbersome just means the customer has to maintain a balance. There is also a difference between a business and residence.
Everywhere I've seen you've payed that months rent by the ~5th of that month or they come after you for interest.