The great irony is putting it in a squatty travel sized container is probably more expensive, and doesn't save nearly as much plastic as you would think.

Having to set up an entirely new production line just to make smaller containers, or retooling your existing production, would likely incur a significant cost.

On the plastic front, the overwhelming majority of plastic in something like that deodorant is in the base, lid, and "pusher" system. Making it shorter only removes a small section of the least-plastic-dense portion of the whole thing.

They could make a smaller one, but the only real benefit would be show & portability, and it would probably come at a premium per ounce