The whole point of the delay is to prevent people from accidentally bumping or leaning on it while driving for some reason. When the shifter was closer (Gen II), this was more common. They could shave a second off, but too much, and you'll get an equal number of complaints for the opposite reason (i.e. I bump my power button on the freeway and coasted to a stop, causing a 20 car pile-up!). Engineers must weigh both sides of the argument, and then Toyota's lawyers (or risk management) get to decide which is safer in the US.