If you type with your two hands in the home row position (as you should), they will be centred around the
j keys on a qwerty keyboard. That means that if you don't want someone's palm to rest on the trackpad and annoying activate it, that you need to place the trackpad below the
j keys to minimise inadvertent touchpad touching and cursor movement.
The picture shown in the question shows a well placed touchpad, whereas if you were to place it in the middle of the keyboard (on that laptop), it would be quite a UX disaster for most users. The touchpad on a MacBook Pro is exactly in the middle, but has a more centred keyboard, which is how Apple get away with it - that and good palm detection.