When the slide rollers drop down the ramp for slide to make a flat floor the rug makes a easy transition for slide
to match up with a tile, hardwood, or rug floor.
When the slide is in, or closed the edge of slide can be easily stepped on with the rug finished slide floor.
If you were to have a tiled or hardwood floor slide floor you run the risk of popping off a tile or crack a hardwood floor edge.
Another reason could be weight of material on slide floor which is about a 5/8" plywood thick floor again for weight reasons.
I am sure the low torque motors could operate the slide but the dressed edge of slide would need reinforcement because of what I have said.
The rug also will hold the chairs for table to the floor so they do not slide around.
Since Newmar came up with the level floor slide years back all level floor slides have been this way before the level floor slide the slide floor was built with a slit step up on to slide.
Some of the kitchen slides are built up now as can be seem here.
With the raised kitchen floor
that can slide over a full tiled floor or wood floor.
Here is a good description
of a full wall slide in use.