I think that back in the day the blades were made of thicker metal and were uncoated, so people tried to freshen up the edge after use.
There are old tales of pressing and curving a blade into the inside curve of a drinking glass and running it round the glass to re-sharpen it or extend the life of the blade.
As has been said, its unlikely to be of much use with modern , coated blades that cost a few pence each. But a fascinating device though and a great collectable.