There are many reasons why Tractor Supply is not in every state. The company has only been around since 1938, so they have not had time to expand to every state yet. They are also a very niche company, catering to farmers and those who live in rural areas.
This limits their potential customer base and makes it harder for them to expand into new states. Additionally, Tractor Supply is a publicly traded company, so they have to be careful about where they open new stores and how much they spend on expansion. They need to make sure that any new store they open will be profitable and not put too much strain on their resources.
Right now, Tractor Supply has stores in 44 states. They are continuing to grow and expand, but it will take time before they are able to reach every state. In the meantime, customers in states without a Tractor Supply can order online or visit one of the many retailers that sell Tractor Supply products.