The early use of kaleidoscopes was for entertainment and the sheer enjoyment of the beautiful images. Still a worthy use today.
Utilitarian uses include incorporating kaleidoscope views and patterns into tapestries, rugs, carpets, wallpaper, fabric and more. Long ago they were used for inspiration in Persian rug designs.
Recently, I've had a school teacher tell me how she uses kaleidoscope to teach her students geometry. What a fun teacher!
Another practical use is for storing/hiding valuables. Kaleidoscopes that have object chambers that can be opened (dry cells) and are sometimes used for safekeeping of valuables.
Anyone who's enjoyed the experience of kaleidoscope viewing hardly needs documentation of the studies demonstrating the stress reduction related to kaleidoscope viewing. Its easy to get lost in the beautiful images, and hard to feel bad when looking through a kaleidoscope.