I think the user decides how much to tip in advance, and the app conveys that information to potential matches. Orders with low tips tend to sit there unclaimed, because no driver wants to bother with that

I’m not sure if Uber does it that way, but Doordash does.

I would say that Uber is a shitty company. Tipping is bs, you should get paid a decent salary and it’s your employer’s responsability to do that.