Touchpoints are "points" of contact between customer and business, but not all customer's actions in an experience can be related to that business.
E.g.: the user wants to buy a smartphone. He goes to the mall and checks the prices of some devices. He likes one model, but doesn't buy it. Instead he leaves and at the end of the day he enters my ecommerce and buy that same model.
In that example, the part where the user explore devices in a physical place is external to my business. Considering this case, should I still be describing touchpoints for each of my customer's steps, even if those touchpoints are not related to me?