Why exactly do you think Jane Austen didn't write proposal scenes in Mansfield Park, Northanger Abbey, and Sense and Sensibility?"
From the post:
So, to answer the question directly, I think that Jane Austen didn't write a proposal scene for either Northanger Abbey and Sense and Sensibility because it simply wasn't necessary (it needed not to be particularly told). In Northanger Abbey and Sense and Sensibility, we as the reader know that Henry Tilney loves Catherine Morland (though she was kicked out of Northanger Abbey by General Tilney) and we know that Edward Ferrars, despite his engagement and supposed marriage to Lucy Steele, loves Elinor Dashwood. So, I think that by the end, we the reader can assume that if Henry Tilney or Edward Ferrars arrived to speak to Catherine or Elinor, that there could only be one reason why: to propose. There isn't a doubt in the mind of the reader that the hero holds a very, very high regard for the heroine, so there is no need to get into a lengthy proposal scene.