Sugar is used in all tomato based sauces to help neutralize the acid and enhance the natural sweetness of the tomato. If you choose not to, that’s fine, but the difference is noticeable. My wife is Italian, can cook her ass off, and makes some of the very best sauces I’ve ever had. As does her father.
Pretty much every top end, hell, medium end, chefs use a pinch of sugar in their sauces. So you may want to avoid Italian restaurants.
As for adding oil when cooking hamburger, it’s only necessary if the meat is incredibly lean. Buffalo meat immediately comes to mind. But we buy our own side of beef, and sometimes we have to add a little olive oil because it doesn’t make enough of its own grease.