Spikes are meant to anchor the speakers to the floor through a carpet so they don't move with the sound. They are also meant to decouple the speaker cabinet vibes from the floor and back. The smaller the contact area with the floor surface, the better. So they will benefit as well with wooden, concrete or marble/granite floors. Just put coin under to prevent damage to a wooden floor.
Speaking about that "smaller contact to the floor, the better sound output" thing, this can be similarly achieved, i think, not only through these spikes but by the use of several wheels. The advantage of using these is that, wheels are more floor-friendly and and more convenient to use because at the same time, you can freely move your floorstanders wherever you want them to be--
I do not have critical ears to hear any sonic improvement though, my satisfaction is just the thought that i followed the principle. Maybe it is more to the fact that it become very easy for me to move them around the house.