Why can't I come in?
The reason why oils do not work is pretty simple chemistry; Pigmented PU coated leather is still after all its processes and protective coverings, hygroscopic, meaning it can absorb moisture. The cross-linked polymer coating is damaged by oils which cannot penetrate into the coated leather surface and bring the much needed moisture to the leather hide (even parking the car out in the sun to expand the surfaces pores with heat doesn't work). In fact, they do the opposite to what you need, sealing the surface so no moisture can get in at all. This in effect is bringing on the opposite of what you're after, leather dehydration.
They also attract dust and grime, trapping it in the surface, helping further damage the top coat. To their benefit, they can leave the leather looking nice and supple, but it's all skin deep. They cannot do the job required, and in our experience should no longer be used on any modern leather.