Paying with just cash?

Because they have no guarantees that the (1) the delivery person will come back and give the store cash you have given them and (2) most of the delivery people do not work for the store they deliver for--they work for independent companies and (3) they don't want their delivery people carrying large amounts of cash around--it's dangerous for them. 

those online places take DEBIT cards as well as CREDIT cards. Debit cards ARE cash--just not bills and coins. Funds come right out of your account directly to the merchant. It's far safer and more secure. 

The delivery person does not work for the merchant, that is why.  

Cash is not a safe or secure form of payment... the guy is a driver not a cashier, they do not carry cash because if they did they could be robbed, so use a  credit card as they are safe/secure

Most deliveries are done by independent contractors who are not employees of the retail chain and are not authorized to take cash.

Usually you can only pay cash when you order from a place that has their own delivery drivers. If you order a pizza, you can pay cash because the driver works for the restaurant. When you order from a big box store, the drivers are private contractors. They are not employed by the store. They are not authorized to accept money or make transactions on behalf of the store. They simply pick up the items and deliver them to the address they’re told. They often make deliveries for many different businesses at once. If you wanna pay cash, you have to go shopping yourself. I don’t understand why you wouldn’t have a card though. If you don’t have a bank account to get a debit card for, you can get a prepaid card. But read the fine print, because some charge lots of fees. I find it very irritating when businesses don’t accept cash, but in this circumstance it makes perfect sense. 

Who does not have a credit or debit card?  And they are usually 3rd party delivery.

Because delivery drivers don't carry cash. It makes them a target for an armed robbery. Get yourself a credit card, they are handy to have.

The person delivering the items is a 3rd party delivery server.  They don't work for Target, Walmart, etc...

-- besides if stores allowed payment on delivery how many people would attempt to stiff the delivery person?

C.O.D. (cash on delivery) was common back in the "old days" before the internet but it was a huge hassle even then.  Not a whole lot of people had credit cards and there was no such thing as a debit card.

Use your checking account debit card.  If you don't have a checking account, I suggest you get one and a savings account too.

They won't take cash because

A  they could keep it and

B someone could rob them.