I can still remember the caption of a cartoon I saw when I was a teenager. I think the cartoon was in Scholastic magazine or some other publication distributed to students. It showed a mother about to read a bedtime story to her son in his upstairs room. The boy says, "Why did you bring that book that I don't want to be read to out of up for?"
The cartoon nicely satirized something our English teachers had been trying to teach us: Never end a sentence with a preposition. The little boy managed to end his sentence with several prepositions, yet he could be understood perfectly. Is there a way he could have said what he wanted to say that would have been both more proper and more clear?
Many writers take pains to avoid leaving prepositions at the ends of their sentences. Sometimes the result is an improvement. Sometimes not.
In his 1990 book The Mother Tongue, Bill Bryson argues that this rule of grammar, like so many others, is arbitrary and foolish. He says the rule's origins go back to 1762 when an amateur grammarian named Robert Lowth suggested that a sentence simply sounded better when it didn't end with a preposition. Later grammarians turned Lowth's suggestion into a rule. "In a remarkable outburst of literal-mindedness, nineteenth-century academics took it as read that the very name pre-position meant it must come before something -- anything," Bryson writes.
Bryson finds rules against split infinitives, the word hopefully and the phrase "different than" equally silly, more a product of conditioning and prejudice than reason.