tfung is right about Biz and First leverage with RTW. With Biz you can still fly A (First) in North America and accrue appropriate base points. With First you get to travel luxiriously and still collect enough miles/points so that the net cost to you (after a simplistic 2c per mile calculation) is not much more than what millions of others pay for much more restricted coach travel. Of course, there are limits on flexibility and inventory control for fare basis, etc.

Most of my RTW travel is leverage on top of required travel. I usually need to touch most of the points for business or pleasure and I add a few segments/stopovers and travel more comfortabley albeit more circuitously.