MDF is also great if you need homogeneous materials (for stuff like speaker cabinets). And for those more than sturdy enough, they are also always protected by some layer.
Yes. I went on a deep dive recently looking for the sweet spot in affordable speakers and subwoofers for near field and home theatre use, and noted that almost every top performer under 1000USD per unit used entirely MDF cabinets. The exception was the Monolith THX series by Monoprice that pay up for HDF and still do well at their price point.
