That’s right. I don’t put anything on my leather to oil, moisturize, treat or clean it. Not handbags, shoes, jackets, binders or boots. In fact, when I buy something pre-loved I usually specify if I am not sure that I do not want one that has been treated with anything.
I have found that handling the items means that the oils from my hands transfer onto the item and it never needs moisturizing. My book artist has said that leather can generally look after itself and doesn’t need much care. In fact his exact words when I asked how I should look after my hand bound book collection were:
You shouldn’t have to do much to it. Tropical climates are dangerous (high heat, high humidity) but short of that it shouldn’t need anything special. Every once in a while I would rub it down with a mild leather cleaner, but you should be careful with that. It needs to be a good one, NOT a leather cleaner for shoes and things.
If I do treat leather (for example very old binders that have been in storage for decades), I use a dash of beeswax. I would never use anything that could go rancid, like coconut oil.