Why is the floor of a parking lot usually covered with a special and slippery varnish?

Question

I just dont understand why isnt it made in the same way as the normal street road.

Answer 1

So oil will not soak into the concrete.
Also it keep dust down and easy to sweep.

Answer 2

It's usually covered in a concrete sealer to prevent stains from drippings of vehicles--wearing shoes with smooth soles is like ice skating on this when it's wet so try to wear a well grooved neoprene sole type of shoe or complain to the building superintendant about this and maybe see if they can install a traction type of coating or sandy coating in walking areas which should have been done in the first place. One good lawsuit from a fall might pay for the repairs.