Here's why:

* Streamlined shapes reduce turbulence: Streamlined shapes, like those of fish or airplanes, allow the fluid (air or water) to flow smoothly around the object. This minimizes the creation of turbulent eddies and vortices, which cause a significant amount of drag (fluid friction).

* Reduced pressure drag: Streamlined shapes create a more gradual change in pressure as the fluid flows past, reducing the pressure difference between the front and back of the object. This pressure difference is a major component of drag.

* Increased surface area for laminar flow: Streamlined shapes often have a larger surface area that encourages laminar flow (smooth, orderly flow) rather than turbulent flow.

Examples:

* Fish: Fish have streamlined bodies that help them move easily through water.

* Airplanes: Airplane wings and fuselages are designed to minimize drag and improve efficiency.

* Racing cars: The shape of racing cars is optimized to reduce air resistance and achieve higher speeds.

In contrast:

* Objects with sharp edges or blunt shapes: These objects create more turbulence and have higher fluid friction.

So, if you want to reduce fluid friction, designing objects with streamlined shapes is a crucial step!