Answer:
Schools are institutions. As such, they run on structure, schedules, and rules.
Many people feel that without structure, only chaos would rule. Strict teachers seek to enforce the rules without exceptions to ensure peace, structure, and order. These teachers believe if you never deviate from the expectations you set forth, there will be fewer classroom problems and increased learning.
Of course, many students dislike strict teachers--- at least at the time. Strict teachers expect more from students. By example, they place higher demands on students to learn and to succeed. And, indeed, most students with stricter teachers do learn, do succeed, and later are even thankful for Mrs. Strict in 4th grade (or whatever grade).