Why does Mary help tom get ready for Sunday school?

Tom is a challenge for cousin Mary to get ready for Sunday School, but she rises to it. First, he hasn't memorized his Bible verse from the Sermon on the Mount. Mary says she will have a nice surprise for him if he manages to do so. When he does, she gives him a Barlow knife worth twelve and half cents. He is so pleased with it that "the convulsion of delight that swept his system shook him to his foundations."

Once Tom knows his verse, Mary has to get him to wash properly, which means he must use soap and water. When he turns up half clean, she finishes the job for him. She curls his hair into a "dainty" effect, which he will get rid of as soon as he can, as he hates curls. She gets him into his good suit, buttons him up to the chin, brushes the suit, and puts a straw hat on his head. She even makes him wear his shoes. None of this pleases him, nor does the prospect of Sunday School.