Can you describe a situation in real life in which a viscous substance would be necessary?

The shock absorbers on a car use the viscous properties of oil to absorb energy when the tire hits a bump.

Oil is forced to flow through small holes inside the shock absorber as the wheel moves up, and again as it moves down to its normal position. Without shock absorbers, the car would continue bouncing up and down.

More energy is absorbed if the holes are smaller or the oil is more viscous.

Also, more energy is absorbed if the wheel moves up fast after hitting a sharp bump than if it moves up slower on a gentle bump, so your suspension can be comfortable over small bumps but still control large bumps well.