wehr is primarily a defensive faction until they reach t3 for their tanks. attacking wehr is pretty punishing if the push doesn't go that well for most allied factions. As soviets, mines act as a defense mechanism that help slow down the wehr defensive creep on your cutoff or fuel if a push does not go as well as hoped and you have a mass retreat on your hands.
pios have great sight range and come with a minesweeper upgrade. why wouldn't you sweep enemy territory. it's just common sense.
The choice is really simple. you either eat a mine with manpower or you eat it with a one-off munition investment.
Thing is, unlike USFs and OKW, ostheer needs his pios for so many more things than those factions. Building the tier structures, repairing vehicles, laying down wire and mines, building caches etc. Guess what, UKF, USFs, and OKW don't need engineers in order to do more than half those things. Also, pios are among the weakest of its type.