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.
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.