Simple fact that the energy dissipates by vibrating the cabinet which creates coloration through resonance. Now if you like this type of sound then more power to you, but I believe that speaker cabinets should be inert with only the sound of the drivers contributing. Dissipating this energy properly is not a simple proposition however. When you check out some of the more prominent speaker manufacturers they spend an enormous amount to time, energy and expense in the construction of the cabinet. Some may disagree but things like wide baffles, thin walled cabinets and parallel surfaces are not things that typically contribute to accurate reproduction. They are also very inexpensive, comparatively, to other types of construction.
So when people discuss the nature of Harbeth sound they describe the texture, tone and natural presentation of the speaker. I take this to mean that they dont hear these attributes on other speakers to the same degree. I attribute this to the fact that Harbeths and similar are coloring the sound in ways that other speakers do not. Some really like this presentation, but I think it is far from natural. My preference is for a transducer that comes as close as possible to the original signal and editorializes less.