I believe it is and think it's due to the fact that you don't want to waste battery life if your vacuuming is interrupted for any reason. Because the suction is so good on these units, it takes a tremendous amount of power and energy, and by having an on/off switch, the user may forget to switch it off when moving furniture, or picking up objects to avoid vacuuming them up - we're used to not turning off the vacuum in these instances, therefore having a trigger forces the vacuum to switch off, thereby saving battery life.