Wirelessly posted (BlackBerry9630/4.7.1.40 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/105)

I actually do believe that the stopover benefit is quite closely tied to the one way option. Ask the AA folks if you disagree. They lost the vast majority of the stopover value when AA switched to one way rewards. Most of the other carriers you cited as offering one way awards also do not permit stopovers, including B6 and WN.

So while it doesn't have to be an either/or scenario (BD does still permit stopovers, for example) in most cases it actually is a choice of one or the other.