Sometimes for whatever reason, like when you might have vegged a plant to long for the size of the pot that the plant is in. You may end up with a root system that gets so compressed that air and water / nutrients can no longer reach many roots in a certain pot, so spiking the shit out of that pot literally allows many of the roots in those spiked areas to get air and water / nutrients that they might never get if you didn't alleviate those overly compressed areas by spiking the shit out of that certain pot!