The answer is simple: consistency of appearance. Consistency in the order, structure, and format of a paper is easier to read and lets the reader concentrate on the content without distraction. Many instructors will take points off for a poorly formatted even if the content is brilliant. Instructors have to read dozens simply because the formatting is a distracting mess!
Another good reason to format your paper properly is it show you instructor that you’ve been paying attention, and understand the importance of a neat presentation.
Margins:
1" on top, bottom, and sides
Font:
Times New Roman, Courier, or Helvetica; twelve-point type for the body of the text is preferable--no smaller than ten-point
Spacing and Indentation:
Double-space all text except the following
The following should be single-spaced internally but with a blank line between items:
Pagination:
Do not number the title page if that is your only front matter. Number pages in the body of the paper and the back matter (bibliographies or reference lists) with Arabic numerals, starting on the first page of the text (page 2 if you count the title page). Page numbers are placed either centered or flush right in the footer or centered or flush right in the header. Be consistent in your placement.
Title page:
Class papers should begin with a title page. Place the title of the paper a third of the way down the page, usually centered. If the paper has both a main title and a subtitle, put the main title on a single, followed by a colon, and begin the subtitle on a new line with an intervening line space. Place your name several lines below the title with any information requested by your instructor, such as course title and date.
Link to more formatting information in the video below.
