Why do economists mostly use optimization in differences, as opposed to optimization in levels?

What will be an ideal response?

For the sake of simplicity and intuition, economists mostly use optimization in differences. Optimization in differences is simple because everything else about the two alternatives that are being compared except the particular attributes that are different can be ignored. For example, suppose that two apartments are both near good restaurants, both have good access to public transportation, and both have a Laundromat down the street. The two attributes that are different, for instance rent and street noise, are compared while ignoring all the attributes that are the same about the two apartments.
Optimization in differences is also intuitive. When comparing two options, it makes sense to focus on what makes them different. Marginal analysis emphasizes this point, by comparing differences instead of levels.