Battery switching with active/passive switches is very uncommon for three reasons.
First off, it requires three poles, which means standard push/pull pots or DPDT switches will not work, and specialized 3PDT mini-toggles must be used. Second, preamps usually put out a pop when powered on. You don't want to hear this when switching to active mode. Third, the current consumption of most preamps usually ranges from hundreds of microAmps with low-power opamps, to a few milliAmps with discrete FETs and such. This is far too low for anyone to care about battery life.