Why does Fred ask Scrooge for dinner even though he knows Scrooge will refuse?

Fred is a good man with a big heart..... he wants to give his uncle a pleasant evening, remind what the holidays are really all about, and he feels sorry for him.... all at that same time.

"I was only going to say," said Scrooge's nephew," that the consequence of his taking a dislike to us, and not making merry with us, is, as I think, that he loses some pleasant moments, which could do him no harm. I am sure he loses pleasanter companions than he can find in his own thoughts, either in his mouldy old office, or his dusty chambers. I mean to give him the same chance every year, whether he likes it or not, for I pity him. He may rail at Christmas till he dies, but he can't help thinking better of it -- I defy him -- if he finds me going there, in good temper, year after year, and saying Uncle Scrooge, how are you. If it only puts him in the vein to leave his poor clerk fifty pounds, that's something; and I think I shook him yesterday."