The hashira were training the demon slayers because there have been no demon sightings for a while. You are a hashira but you're to young to train others

Obanai: that's the way its gonna be. Deal with it. Sanemi: I won't go a single bit easy on you. Muichiro: .... Tengen: don't worry. I'll make sure that you are having fun while doing it. Kagaya: you will be doing the corse with tanjiro, inosuke, and zenitsu.