It is also extra expense and complexity in a build, which raises retail prices, in order to satisfy maybe less than 0.01% of the potential buying public. That one in 1000 or less...who might tear the speaker apart and modify it.
This^^^ Duh!
Economics, the dismal science, apparently no longer taught or everyone would be able to figure this out.
The compartment idea is nuts. A better idea is to put the crossover outside the speaker cabinet. This has the added advantage of improving sound by removing the crossover from the high-vibration environment of the speaker cabinet. But again, the improvement is so slight compared to the cost it'll never happen. Except among modders. But they already know and have been doing this for years.