The angle of approach in a plane changes the effort needed to cut and the likelihood of tear-out from the surface. These are cross purpose factors, meaning that reduced effort and increased tear-out results from lowering the angle of approach and increased effort and smoother cut from a steeper blade angle. Like other twin factors, and tool steel hardness and toughness comes to mind, the trade off between them results in a compromise of acceptable levels in each. Tool steel accomplishes this by tempering the excessive brittleness by reducing hardness a bit. Planes change the angle of approach.
When maximum shaving to quickly reduce stock size is desired, a plane with lower angle of approach and a somewhat larger throat opening to prevent clogging is employed as in the scrub plane. The smoothing plane has a steeper blade angle and tighter throat.
The trade-off in ease of cut and surface finish has resulted in the general approach angle of 45°. When greater control over surface finish and avoiding tear-out are primary, a smoothing plane with the blade at a steeper angle is employed. Some have 52°, some 55°, some 60°. This little plane employs the possibility of a 60° approach for fine work, and a 90° option when even that would tear the surface in some wild grain wood. How could that be? The change is effected by turning the blade around so the bezel, or ground surface, faces forward. The 60° bed plus a 30° bezel gives a 90° approach. It is now a scraper plane.