A currency only has value because the users of it 'believe' or 'trust' it has that value. You don't want your boss to pay you in Myanmar Keyat (yes, those exist) because you have no knowledge about it, you won't trust it.

This link gives a nice intro: https://www.thoughtco.com/why-paper-momey-has-value-1146309

I agree your parents like their Franc better. But just think about the hyperinflation in the Weimar Republic. The value of the paper was worth more that the money itself. People started weighing money:

https://keripeardon.wordpress.com/2013/06/01/wheelbarrows-of-money-and-the-weimar-republic/

If you look at it that way it's not that hard to look inverse at it and think that coins have value. I don't see them replacing money, I see them side by side.