Personally, if I had 11 speakers, I would just get the A8A and not worry about any other amps.
One of the main reasons for owning any AVR is convenience - not having to worry about buying any external amps.
So many people probably just want an AVR to power all 11 speakers (RX-A8A, X6700, SR8015) or all 13 speakers (Denon X8500).
There are other personal factors that some of us might feel uncomfortable to divulge on open forum.
There is no "right or wrong" or what "makes sense or doesn't make sense". We don't have to justify to everyone that we made the "right decision" that "makes most sense". It's just personal preference.
At the end of the day, if you feel good about adding an Outlaw amp to your AVR, then it's the right decision for YOU.
And if others feel good about just getting the A8A, X6700 or SR8015 to power all 11 speakers, then that's the right decision for them.