What is the theory behind speaker floor spikes?

More specifically, why would I want to mechanically couple my speakers to my floor? I have wood subfloors on pier & beam construction (no concrete). Over that is 2 layers of carpet pad and then carpet - in all, close to 1" thick.

Seems to me that with my wood floors, I'd be introducing vibration (jitter?) into my source machines by tying my speakers to the floor.

In my case, wouldn't I rather just set the speakers on the carpet and let them float there?


-Jon