But if you calculate the acceleration without the graph, you are explicitly stating that the y-intercept is zero---which it might not be. So there are some actual reasons for making a graph.

Learn the uses of equations and graphs of motion and how to determine other aspects of the motion of objects. BBC Bitesize Scotland Higher Physics revision.

Find the acceleration of the sledge when t = 6 s. Draw a tangent to the curve at the point where t = 6s and draw two lines to form a right angle triangle.