Slipperiness is a problem that arises occasionally on leather items. Furniture leather may cause you to gradually slip off the sofa or chair while sitting. Slippery wallets can slip out of the pocket when sitting down, and motorcyclists can lack the necessary grip when riding on a slippery motorcycle seat made of leather.
Smooth leather with a finish is often made slippery in the production process in order to reduce mechanical damage during use later. Usually this is done by additives in the top coat. Resistance generates friction and this can lead to faster traces of wear due to abrasion on the leather.
As long as the slip is not annoying, it is a good protection against abrasion. Where the slipperiness is disturbing, it can be mitigated by suitable care products. Some waxes and waterproofing products are helpful ingredients. Waxes are generally very blunt and slow the slipperiness. Also surfboards, ski and snowboards are waxed, so the "grip" improves. But always clean the leather first. This can sometimes help substantially.
But there are also leathers, where slippery is desired. For instance, ass leather in the former mining industry was used to protect the bottom when sliding through holes in small tunnels by sitting resting your bottom on a piece of "ass leather".