im left wondering why so many owners & manufacturers alike make a consience choice to let this information slip awayI can give a few reasons.
It's difficult to design a full-range passive spkr and the result is invariably very expensive.
It's also very bulky -- to go down to 30Hz & below (i.e. you're best using large drivers, transmission lines, etc)
It's often very difficult to drive full-range spkrs well, so amplification becomes an issue.
It's best to biamp -- but how many a'philes will consent to having 4 channels of amplification.
It's also difficult to reap the benefits of a full-range spkr at both moderate volume and higher volumes: in order to perceive bass at lower volumes you need to equalise it carefully (boost the spl and make sure you're not creating phase anomalies) because we're less sensitive to lower freq at lower spls. If you play that same spkr loud, the bass will be perceived as overwhelming (because our ears, at higher spls now, are more sensitive to the lower register).
A trade off/compromise, etc, I suppose! But I too like to be able to go down to the 20's...