Why didn't Warren need a hired man?The Death of a Hired Man.
In "The Death of the Hired Man" Silas the former hired hand has come "home" to die. In answer to your question, it isn't so much that Warren doesn't need a hired man; it's more that he doesn't need this hired man. Silas has worked for Warren before and, while he is a decent worker, he has been less than faithful to the job--and the man.
He bundles every forkful in its place,
And tags and numbers it for future reference,
So he can find and easily dislodge it
In the unloading. Silas does that well.
He takes it out in bunches like big birds' nests.
You never see him standing on the hay
He's trying to lift, straining to lift himself.
But, during the harvest time when workers are scarce, Silas was bribed away with a little pocket money. Once winter hit and there was no real need for workers, back he came. Warren has told him that if he left again, there would be no coming back.
What good is he? Who else will harbor him
At his age for the little he can do?
What help he is there's no depending on.
Off he goes always when I need him most.
There it is. From this it's clear Warren has not only been disappointed by the old man, he's also been hurt. There was obviously a relationship of sorts between them, since Silas comes here to die rather than to his brother, only a short distance away. This is his home, whatever may have been true in their past.