I think there's a difference between a typical website chat window and how many people would use ChatGPT. The latter has tables, images and links which is enough to build up comparisons, order sheets and then ultimately have a format for confirming a purchase. I use it a lot for doing basic home construction comparisons (materials, volumes, etc) and could definitely see it getting to the point that it organised an order for me to submit, and eventually to where the submission and payment were within the chat.

A voice assistant doesn't give you that option to review, but maybe it'd work for ordering fast food. A small chat window could grow to work for simple purchases like takeaway food or small hardware, etc.