Contact or lining paper for shelves has, it seems, become a thing of the past- it's something you'd see on Mad Men, not in a modern home. It's used to make cleaning the inside of wood cabinets easier, and to prevent cabinets from getting too dusty. Nowadays, contact lining is much less common than it used to be. Some people don't like the paste residue it can leave on their cabinets. It's generally not considered necessary, as long as you regularly clean and dust the inside of the cabinet. Hope this helps.
Call me old fashioned, but I have to agree with your mother on this one. My wife has been homemaker for 26 years, and she's always lined the cabinets. It saves her a lot of trouble with cleaning and dusting, and she uses patterned paper that spices up the boring cabinet surface.