OK, but then why do most bass speaker enclosures have a reflex port?

I was always told the enclosure channels the sound energy, hence the need for a port to allow the speaker diaphragm to move air on the return movement. I was under the impression that this was why reflex ports had exponential horns built in for "impedance matching", and that sealed enclosures were a "bad thing" due to the effect of the case pressurising on a return movement, which added a damping factor to half the amplitude of the sound waveform.

Surely with bass tubes and reflex enclosures being so popular, this isn't so?