Ballpowder, perhaps a little history lesson will enlighten you as to why things have evolved the way they have in Benchrest.
Years ago, 22's dominated the Sport. there was no such class as Sporter, which requires a caliber of .23 or above. When the NBRSA institued the Sporter Class, it was understood that 6MM would never be as competitive as a 22 in 100-200 Benchrest. But, then came the 6PPC, and the Gods went mad. Suddenly, shooters were winning LV and HV with Sporters, and sooner or later, the vast majority of shooters simply said, "why even put up with the hassle of shooting two entirely different calibers, when I can simply build a Sporter, and win".
Now granted, that is a rather simple explanation of events that happenned over a 25 year period, but the reality of the situation is still there. At any Registered Match, including the Nationals, you can count the number of shooters who are not shooting a 6MM on one hand, maybe two on certain years. In fact, I do not even know of a shooter in our Region who seriosly campains a 22.
Why?? Simple. This is a competitive game, it is an expensive game. Many shooters expend thousands of rounds a year, and the difficulties in just keeping one set-up in a competitive state is difficult enough. So, since "Sporter" is the lowest class, and can be shot in any class, and a 10.5 pound Sporter can win on a regular basis in LV and HV, why not just go that route.
Since that is what 90 percent of the NBRSA Members do, it seems to be a sound train of thought..........jackie