What purpose do linners serve in a handle?

[MT Borg]

I use a little acrylic paint in the epoxy that matches the liner to fill in any possible voids in the scales.
I also let the colored epoxy fill in any tang filings.

 

[noseoil]

It's just that little extra detail that changes a ho-hum appearance to something more pleasing to the eye...

 

[Diego_B]

To make your knives look pretty

 

[Bigfattyt]

I've been using Renaissance wax under the scales of my CPK's. I hope it works out well. I do check them every week or so and I haven't seen any rust yet.

Why would you be checking under the scales every week for corrosion?? Are you storing the knife in a vat of salt water??
All you are doing is wearing out your attachment hardware.

You could ignore the tang for 100 years on that CPK knife and not have any issues.

I have carbon steel knives from my grandfather that are at 100 years and still going strong. The scales have never been removed. (Thoug they have been used in the kitchen and put away wet many times, used to process the cows and pigs on their farm...there is some corrosion, but they will still be going strong when I hand them down to my sons.

As to OP, color, looks, and handle scale translucency, adding thickness have all been mentioned.

I've also seen it noted that for natural materials like bone/antler/horn it can help keep them stabilized and cut down on chipping/finishing issues when sanding the edges.