The Simpson family, like most in America, would not be able to function without the presence of a figure who gives gets everyone through day to day situations. Marge does all this and more, puttin up with Homer's drunkeness and Bart's mischief making without completely losing her mind. Althoug Marge has been for the most part a stay-at home mom, she has demonstrated that she has the intelligence to work, in the episode she becasme the top employee at a real estate agency, but chooses to stay at home.
Marge can be seen as the perfect representation of a typical housewife who spreads unconditional love to her husband and children and hardly ever utters a cross word. All the while, Marge supports her children's activites and is always patient and gives them another chance (even after Bart took a car on a road trip). More then any other trait, Marge can be interpreted as a model/ideal American wife and mother becasue she loves all of her family members without reservation.