...Yes it would be useless, if your intended needs included carpooling which I would consider a typical usage case for a car. The typical usage case for laptop is using multiple ports.
Eh... I don't think this is any more true than saying that the typical use case for a vehicle is hauling cargo. For many, perhaps. For many others, not so. Hence bicycles, motorcycles, subcompacts, etc.... are very popular vehicles for many people's use cases.
I haven't even purchased an adaptor for my MB. I've only used the port for charging, and wireless has provided a perfectly suitable way for transferring the data I need transferred.
That won't be true of others, of course. They'll need ports for thumb drives, external HDs, optical drives, etc.... Some people need trucks, others don't, and would prefer the economy and portability of a motorcycle.