Reply to "Plywood then Homasote or vice-versa?"

I don't understand why people bother with the expense and effort of plywood under homasote.  I built a layout in the 1990s (now gone) where I put homasote directly on the benchwork, did not use plywood at all.  It worked fine, did not warp and was up for over ten years, and it was very humid in the summer.  I did have supports on perhaps 24" centers. 

Bill