I want to know why I have to pay return shipping on an item that was listed incorrectly or damaged.

Buyers are always responsible for return shipping. Good sellers will reimburse return shipping when the mistake was theirs, however they are not required to do so.

Contact the seller and ask. You still have the option of leaving feedback.

Sunny “Why do people keep running over a string a dozen times with their vacuum cleaner, then reach down, pick it up, examine it, then put it down to give their vacuum one more chance?” - Unknown

John, it's my opinion that a really good seller, if he believes you are correct about the item being not as described, will refund you for the return shipping. His practices in that regard should show up in his feedback and star ratings from buyers.

Consider that eBay usually takes the word of the buyer when the buyer says it is not as described and the seller says that it is.  Obviously either they disagree or one is lying, but eBay--with no way of knowing which is right—takes the buyer’s side.

This policy could be dreadfully abused if the buyer weren’t required to pay return shipping.  Have you ever watched a woman in a shoe store?  She may try on ten pairs of shoes before she decides which pair she likes best.  On eBay, if she didn’t have to pay the cost of the return, a dishonest person could easily do the same thing.

I don't know that this is the reason behind eBay's policy, but it may very well be.