Vibration and where you sit are the reasons for a speaker stand. A speaker stand that has been spiked through a carpet or is on a solid base of granite, filled with sand or atabites and either spiked or blue tac'd at the top to the speaker will provide a solid platform for the speaker. The aim is to reduce and dissipate vibration from the speaker. The reason for that is that the enclosure becomes part of the sound.
You mentioned having the speaker hovering. You go another step further and literally just have the speaker cone hovering.
To get round that speaker manufacturers either minimise the cabinet vibrations and/or use them to help produce the overall sound. So you get fully enclosed speakers, ports, curved cabinets, horns etc.
A speaker stand also helps the sound by making it easier to position the speaker. You want your eyes to be roughly at the level of the tweeter when you sit. You also want to be sitting in the sweet spot between the speakers where the stereo sound crosses and is at its clearest. Finally you want to affect the influence of your room walls. Some speakers sound their bast with their backs to the wall, others are better sitting out from the wall. Most speakers are best kept out of corners.