Sorry, I'm slow I still don't get it. Zero displacement then means he's doing straight round-trips where he's going back to where he started? If so, why does that matter? I'm missing something basic here.
I believe that what he's getting at is that most people are going to start out from home, travel to work, and end the day traveling back home. There may be stops during that for shopping, or round trips from and back to work for things like lunch. But at a high level it is "go out from home in the morning, come back home in the evening, and then do the whole thing again the next day".
With this pattern, you want some form of transit that will reliably be there for you in the morning, every morning.
Owning your own car, motorcycle, bike, or scooter works for that. It's yours so it will be there for you whenever you want.
Public transit can also work, if there are stops or stations near enough to your home and work and it operates on a schedule that fits yours.
His point is that transportation services like Lime, where you pick up scooters from whatever semi-random place the last user left it and you are supposed to stay within some specified area don't work well for the home => office => home cycle. There may not be a scooter near your home in the morning, even if you happened to have left one there the night before. For a lot of people, home will also be outside the service area, so taking one home would incur penalties.
But if you have you own car, motorcycle, bike, or scooter, and you have to use that to go to work, then using that for all your other transportation while in the city is probably going to make more sense than renting a Lime scooter.
I think he's being a little too pessimistic about the market for something like Lime. I've worked at places where I've driven my own car in, but would have been happy to have something like Lime while at the office for things like going out for lunch, because lunchtime traffic was pretty bad around the office but there weren't any good lunch places in easy walking distance.
strictly speaking, displacement is a vector quantity, as opposed to distance, which is scalar. if you drive a mile from your house then turn around and go straight back, you've traveled a distance of two miles but your displacement is zero.
