Hey Americans, why would you tip your server but not your Uber driver?

I’m Canadian and i take taxis every morning and always give them a tip. If I’m at a restaurant I would give them an even bigger tip than I would an uber driver. I understand tipping at restaurants because every place has different costs but I still get the same service from every Uber driver. It just makes me wonder why even if we are getting same or similar service from Uber drivers why don’t you give them 15-20% of the bill. Of course there are exceptions like if you are late and the driver doesn’t help with your bag he deserves less but why don’t you automatically give him 20%