From a spectator standpoint, I'd agree.Pro sports franchises have been bolting for greener pastures for decades, with no particular pattern. Big Ten country has lost its share too - the Braves moved from Milwaukee to Atlanta, the Cincinnati Royals became the Kansas City-Omaha Kings, the North Stars left the Twin Cities for Dallas and the Browns snuck off to Baltimore under the cover of darkness - to name a few. Texas might be the most football-crazy place in the world, but it lost the Oilers to Memphis and then Nashville.
I agree that Pac 12 territory, in general, is not nearly as much into college sports as Big Ten, SEC or Big 12 country. But pro sports fare pretty well in the West, a couple of departures notwithstanding.
From a participant perspective, the PAC 12 has 529 national championships, which is over 200 more than the next conference (B1G).