Forget all the rubbish about reducing speaker movement.
No the real reason is, spikes are wife friendly! Without spikes, speakers leave very nasty indents on the carpet.
However with spikes, only small holes are created, that can easily be removed by the judicious use of one's finger; Vahalla i.e. no nagging.
BTW I have not got any nagging sound files to comply with TOS 8!
(http://i.imgur.com/qv7orry.gif)