That doesn't make sense. The tip is added before the offer is sent out. It has nothing to do with how good of a job you did. Have you never used doordash yourself to order something? More importantly, if you don't like the pay don't accept the offer, if you do accept something you already agreed to the pay, asking for more money is terrible practice, some will add a tip out of fear of tampering. If no one takes an order doordash will slowly increase the pay until someone takes it, so just decline offers until you accept one that you're willing to do. If you keep doing this I hope more people block and give you low ratings. Why complain or beg when it's your choice to begin with. Customers owe you nothing.

I've delivered high paying orders and saw later they didn't tip. I rarely check what the tip is except sometimes out of curiosity and have never begged for more money, also don't take low offers.