Answer:
He wants some peace and quiet so he can think
Explanation:
According to the book The Night The Bed Fell, the father decides to stay in the attic so that he can get away from everyone else as they were all acting strangely.
However, this decision will come back to bite him because while in the attic, the bed fell on him.
Prior to seeing their father's skill as a marksman, both Jem and Scout shared the perception that their father was older and couldn't do much of anything other than read and work. Jem especially was flabbergasted at Atticus's ability to kill the rabid dog in one shot, even though it was "a little to the right. . . .Always was." Miss Maudie, who addressed Atticus immediately after this episode as "One-Shot Finch" was delighted to tell Jem and Scout that "Atticus Finch was the deadest shot in Maycomb County in his time. . . .Guess you'll change your tune now." Like many children, Scout and Jem had never really given much thought to what their father's life might have been before they entered it, and the idea that he might have been young once was probably something new to consider; additionally, Atticus had never spoken of his talent in this particular area.
I hope i helped have a good easter! :)