When a shop says that the delivery charge is not a tip, what then is it? a surcharge?

What they're saying is, the delivery charge goes to the company, NOT the driver.  So if you think you're tipping the driver $5 or whatever it is, you're not.  Whether you choose to tip on top of that is up to you.

Just another way of increasing the price.

If they call it a delivery charge, then it's a delivery charge. That is neither a tip or a surcharge. A tip is just a reward you feel like offering whoever served you.

It is the charge for getting the item from the shop (point A) to where you want it delivered (point B)

It will include running costs and fuel if a vehicle is involved and the wages of the person delivering it. There may also be an element of profit.

It's part of the price of getting stuff delivered. If you think the driver deserves a tip, you pay that in addition to the delivery fee.

An expense by the shop passed on the customer.  Nothing unusual.  It is just business.

Another excess fee places charge to nickel and dime you to death.

TECHNICALLY, it's a fee to compensate the driver for their gas and wear on their vehicle... Essentially, a way to make sure the driver is fairly compensated for their own expenses.

In reality, most businesses just pocket the money and the driver relies on tips.

Just another way of increasing the price.