I suppose it is because they are designed to do different things. A proper music speaker system is designed to reproduce musical performances in a lifelike manner. A Home Theater speaker system is designed to produce sounds like asteroids crashing into planets, 100mph car crashes, and jet aircraft flying overhead in close proximity. Very little, if any, aspect of Home Theater has anything to do with music reproduction. Since this is the case, the speakers should be designed differently, since they have very different purposes.
H/T vrs Music speakers-Why the difference?
It seems as if most H/T speakers designed for use as the main fronts have a different driver configuration than speakers designed for 2 channel music. This difference is especially noticeable between the two types offered within the product lines of companies like Dynaudio, Silverline and Von Schweikert (3.5 I think) The H/T offerings by these companies have a Dunlavy type driver array (D'Appolito?) whereas their music speakers have a more conventional array. Anybody know why the difference? Whats the difference between a Dynaudio Contour T2.5 and a 1.8 Mk II? or a Silverline Sonatina II and a Corona II? They seem like VERY similar speakers with the drivers placed differently.