Is there any reason to not build heads entirely with reticulated or dry-fast foam?

Availability and pricing aside, it seems like reticulated (speaker) foam is superior to regular upholstery foams you buy from the fabric store.  It lets air and moisture pass through it with no problem, so you can wash pieces without worrying about mildew.  At least that's what I've been told!  Is there any reason why I shouldn't start buying the stuff in bulk?  Is there a reason to use regular polyfoam instead?

Here are some of the foams I'm looking at.
http://www.fabricempire.com/dry-fast-reticulated-foam-sheets-fabric.aspx
https://www.foambymail.com/speaker-foam.html