No judgement from me towards anyone who uses a microwave like this. But that's not a good argument. If you want to get pedantic, the one-time inconvenience of going to the store will be made up for by the hundreds of small conveniences of using it later.

In general I don't think it's fair to think about the inconvenience of buying a thing. Even online reviews, which often complain about shipping times which has nothing to do with the product, don't really complain about the inconvenience of having to buy or order something. It's not relevant.