One word: winelib! There are several large open source projects that, for one reason or another, targeted Windows at their genesis. Many of these projects are quite old, well established, and would take many man-centuries of work to rewrite for native Linux systems. Enabling wine on ppc64 gets us a cheap way to allow these projects to run (when built from source) on ppc64 systems via winelib.
Initial compilation hurdles fixed. Wine builds and installs but the old 32-bit ppc thunking is incompatible with the new 64-bit systems, and crashes immediately on start.
Monolithic (will be split when closer to merge):