there's much more science into water chemistry than you think.
pH is just ONE of many different properties that exists in water that affects your fish and it's acclimation to new environments.
ideally, any pH change should be avoided. but if it must occur, then you'd do it slowly.
but as for acclimation, it's really not practical to buy a new fish, setup a tank that's exactly like that of your fish store and convert it slowly to that of your tanks. so, common sense tells you that you'd just have to do the next best thing, which is to drip approximately an hour or so.
to be honest, I worked at a fish store when I was back in high school, and we bring in a truck load of fish twice a week. we don't even drip the water for freshwater fishes, we simply float the bag for half an hour and dump the fish in.
and the fishes do great, even start feeding in less than a few minutes; in most cases.