Think of this in terms of Pounds Per Square Inch.
Concentrating the weight of the speakers on those tiny spike points means the full weight of the speakers is concentrated on a tiny fraction of a square inch.
But generally speaking, when you use the top speaker spikes, the speakers rest directly on the spikes.
The Spikes both floor and speakers, also give you some ability to level the speakers on an uneven floor.
However, not everyone like the Carpet Spike and not everyone likes the Speaker Spikes. Many use BluTack because it has some limited glue ability. It will make the speakers stick to the stand, though much like a Post-It, the bond can be broken. In some cases the BluTack,
which is really just a variation of common Poster Putty,
can react with the speaker finish and discolor it. Though being on the bottom, no one will ever see it.
You can also get assorted Vinyl Feet
(dots, squares, etc...) at the local hardware or building supply store -
And, if it matters to you, you can also get similar in Felt Feet -
Further many Fabric Stores have an assortment of flexible clear Vinyl Sheets
that could be used to cover the top shelf of the stand, and act both as a cushion for the speakers, and to hold it in place -
The advantage to Poster Putty or Blu Tack is that it cause the speakers to stick to the stand, so if it is bumped, the speakers is far less likely to fall.
Just a few thoughts.