Hot and Dry
On a hot day in the sun, with the windows up and doors closed, your cars interior can hit temperatures of close to 75+ degrees, with surfaces the sunlight hits getting even hotter. It all helps to create one of the worst environments for your cars leather.
For PU coated leather to stay, soft and supple, not break apart and crack or become brittle, it needs to be constantly hydrated. The only thing that can help is a water-based product. The water vapor molecules are the only nourishing item that can penetrate into the coated hide, unlike any other oils, balms or other snake oil, that all sit and seal the leather surface, actually making the whole drying out process more pronounced. Of course if the water molecules can get in, they can also get out, which is what happens on those hotter days as the heat begins the process of evaporation. So you can begin to understand why it is critical over the hotter months of the year to keep re-hydrating weekly, if your car sees a bit of sun.