There’s no reason for that. There’s no shortage of space in transit, and plenty of ideas for making transit comfortable (inflatable habitats or reusable cyclers, for example).

> There’s no reason for that.

It's the exact same reason as it is now for air travel...profits. It doesn't matter the size of the ship. If you can squeeze the space to increase the number of occupants per flight on the same ship, you increase revenue. That's all corporate bean counters will care about. I would not be surprised if they hire a similar team that airlines have now that get paid to specifically redesign seats to squeeze more in per flight.

There's no air in space, so there's no need for aerodynamics. Inflatable structures allow for quite a bit of volume during transit without much impact on structural mass. This is not analogous to airplanes.