I saw a video about these recently. Some think they may have been a kind of throwing weapon, but nobody really knows. Many of them aren’t made in a way that a rope or string could be fitted around them.
Scrimshaw in stone. Art done for the sake of art, not all that different in its way from, say, traditional patterns woven into cloth or wood carvings for ornamental purposes.
Much too expensive in terms of time and effort expended to be used as weaponry, when a simple river rock of that size is both much more available and fitted to the hand.
When men were hunting from trees, the stones were used to disable/kill the prey and used to dissuade larger predators from also climbing up the tree (bears).
On the other hand many of the ones shown would hold a rope or string for a bola.
Early golf development, aerodynamic ball testing
I think they were made for crushing grains and pulping foodstuffs