The majority of sellers on eBay are just your neighbor, someone's mom or dad, grandparents, disabled people, just regular people selling items to keep the lights on and food on the table.
Think of how it is for you in your job when you make an error. Think about how you would like to be treated. Was the error so horrible that you deserve to have your pay docked. Was the error so bad that you deserve to be temporarily suspended. Or did you really screw up and deserve to be fired. It's no different for a seller. DSR can and do SIGNIFICANTLY impact a sellers ability to sell on Ebay. And the rules are so strict that even 2 buyers out of 100 transactions can bottom out a seller in the searches if they hit the DSRs while leaving FB. Think about that next time you feel like leaving negative feedback. And sellers think about that before you even join eBay as you'll spend your whole time being at the mercy of buyers and kissing their butts till you can't take the degradation anymore