Wet sponges [0] for people counting money were a very common sight some decades ago before money counting machines and mostly electronic payments. Probably still being used just not so obvious anymore. Regardless of age fingertips will eventually get too dry as the paper absorbs all the moisture and flipping pages or separating banknotes becomes hard.

For touchscreens dry fingers are also called "zombie finger" [1]. The screen registers the too minute change in electrical field as noise and rejects the touch event. Some sweat (but not too much) on the fingers makes all the difference.

[0] https://image.shutterstock.com/image-photo/sponge-finger-wet...

[1] https://www.consumerreports.org/cro/news/2015/06/zombie-fing...