Because lyft plus is bigger cars. Because plus size clothes are for bigger people. Everywhere but CA the service is called Uber select. So the real answer.....Uber is stupid and named their service wrong.
The fifth one goes in the trunk. It's because Lyft Plus is for 6 and most other Uber cities are smart enough not to confuse the Plus and XL and have labeled it Select. Just the morons operations peeps in Los Angeles and San Diego with their heads up the arses screwed this up. That paired with most people that use Uber are just idiots. If they can't place a pin then how do you expect them to know something more complicated like what type of ride they need?