You say that as if it costs too much. In fact, given what it does, and what analogous cinema cameras cost, this is a bargain.
I wouldn’t be surprised if a majority of buyers would prefer more available features (and a longer hardware lifetime) and having to pay for them instead of fewer features for free.
A camera sensor doesn't care what shape the image is, as it only cares about if photons are hitting it or not. Yes, you can tell the camera you are shooting a certain aspect so that it doesn't energize parts of the sensor that's not needed. So some additional dev costs to add that feature.
What else am I missing?
Besides the lense is probably more expensive than this camera. It’s not really that expensive given the industry.