UberEats still allows it, I believe. But people abuse that feature by “tip baiting” someone to take their order, then removing the tip after the driver has already spent the time, gas, and effort to deliver it. The driver could spend an hour on the order and only make $2.50 during that time, minus the cost of gas. Happens a lot with orders that are several miles away from the restaurant especially, because no one wants to pay enough to make the trip worth it for the driver.