Yes, mattresses are a big area where you have to think about viscoelasticity. Another area is eye care.
I visited the eye doctor recently and I complained about having dry eye. He said they have these collagen type plugs that they can insert in the eye, and they help retain moisture.
The plugs are basically viscoelastic devices because they have to conform and bend to the shape of your eye, fitting perfectly and becoming almost totally invisible.
He recommended that I try them; however, the thought of putting anything in my eye at the moment doesn’t sit well with me. I’ll stick with my eye drops for now.