Dickens begins A Christmas Carol by introducing the reader to Ebenezer Scrooge and quickly conveys the type of individual Scrooge is - "A squeezing, wrenching, grasping, scraping, clutching, covetous, old sinner!"
While not giving a direct description of Bob Cratchit for some time, Dickens clearly implies the way in which Scrooge's personality shapes the relationship between the two. Scrooge tolerates no waste of anything and defines waste as meaning anything above the barest minimum. Therefore, Scrooge isn't inclined to permit Cratchit to indulge in luxuries like adequate coal for the fire. "Scrooge had a very small fire, but the clerk's fire was so very much smaller that it looked like one coal."
In the same way, Scrooge disliked being forced to give Cratchit a full day away from work, but with pay even though no work was done, in recognition of Christmas. Scrooge considered it highly unfair that he didn't have use of his employee for every minute of time for which he was paying.
"It's not convenient," said Scrooge, "and it's not fair. If I was to stop half a crown for it, you'd think yourself ill-used, I'll be bound?...And yet...you don't think me ill-used, when I pay a day's wages for no work...A poor excuse for picking a man's pocket every twenty-fifth of December!...But I suppose you must have the whole day. Be here all the earlier next morning."
Scrooge didn't want to relate to Cratchit. He wanted Cratchit to do his work quietly and cheaply.