As far as I could find, they served no practical purposes. Is there any reason for them besides status and "spikes are cool"?
Hi, you may be interested in a couple of images of the spike being put to in use in these threads
What was the purpose of the spiked finial on the tops of Pickelhaube helmets used by Germans in WW1?
Did the early WWI pickelhaube offer any sort of protection?