I don't think it's widely used in Word/PowerPoint etc. because it's not widely known. Also I see it's just not supported in the Mac version of PowerPoint, which is a bit of a shocker.

Given the size of modern disks, and even Internet speeds for e-mail attachments, if I were Microsoft I'd be tempted to turn it on by default, with subsetting enabled, but historically that hasn't been done because of the effect on file sizes.