The real issue is that the hood on the Sienna is basically the same height as the one on most crossovers, because that's the nature of a vehicle with tall roof (necessary for cargo capacity). The hood/windshield has to ascend quickly to reach that height unless you want the hood to be longer, but a longer hood would negatively impact the ability of the driver to see children directly in front of the vehicle.

A lot of this is also dictated by the safety requirements for vehicle collisions, because a vehicle where the front of the hood is lower than the bumper on the other vehicle (which could be a pickup truck) causes the hood to act as a ramp instead of a crumple zone, and then the occupants get hit in the head by a truck.