I understand how that could come across as strange - in a way it is probably because of the Airbnb platform. Everything is very standardized, and there isn't an easy way to, for example, have a toggle where the guest could select breakfast if they want it or not, or view some kind of menu and select the items they want. So if the host is planning on offering something beyond the basic cheerios and milk, their only option is to ask you if you are interested which is awfully direct and might put you in a position of wondering if they will be put out if you don't have breakfast or something like that. Meanwhile, if they roll the cost in for every guest, their room may not be competitive with others in the area for people who aren't as interested in breakfast.
My guess is that it is probably someone who genuinely enjoys cooking and would like to provide something beyond the standard, and so they are using the tools that are available to them on the Airbnb platform to plan in advance for your arrival. If they waited until you were already there to ask, they may not have enough time to go get everything they need. I would recommend that you consider the offer and make your choice based on what you truly want to do, as that is likely their intention.
