The requirements for the material of the speaker are uniform and high density, and then low cost.
The MDF is just right, the density of man-made materials is uniform, and the density is also more appropriate.
There is no way for solid wood to have such a uniform density.
In addition, many people think that plastic boxes are the worst, and there are even some brands that have no advertised that they only advertise that they say wood. For example, a certain Baidu searched first place. They have no other brightness except wood. But in fact, plastic speakers are the best, with high density, uniformity, and easy molding, but the cost is too high.
Don't use those small plastic boxes as the standard. To make a plastic box, the thickness will be much larger, and there are many supporting ribs inside.
Then look at how much a ton of plastic costs. Larger molds are also very expensive, with large thickness and volume, and the requirements for injection molding are greatly improved.
The cost is not high enough for sales.