Why Veneer?

Veneer over particle board is far less expensive than solid hardwood. Manufacturers claim that the lesser resonance of the particle board is an advantage also.

Particle board (MDF, HDF) is more consistent and practical.

(average and better quality, not the cheapest stuff at Home Depot) particleboard is denser, more consistent batch to batch, CHEAPER, and doesn't warp or crack as it dries.

Particle board and Medium Density Fibreboard (MDF) have better and more controlled (i.e., consistent) damping than regular wood and are a whole lot cheaper, especially in the larger thicknesses common in high end speakers. It's also much easier to change the visual appearance with veneer, the basic structure is the same, just the last 1/32" is different. I'm sure the speaker would sound much different if made entirely of Oak versus Cherry. Also, the more exotic woods are frightfully expensive and in such short supply that they almost have to be used in veneer form.