It's like explaining that the cash they see is backed by the government, making it widely accepted, while cryptocurrency may not be as familiar or backed in the same way.
Cash written by hand on paper and signed by the real person with whatever Value they offer is credible. The government cash is not really backed by the government - it is all illusion.
"Valid point! Handwritten cash has personal value, but government currency's trust lies in its widespread acceptance and legal backing. Interesting debate!