Friction is the correlation between clamping force and momentum. You have to have controlled spread of friction to know how well your parts are joined. In physics, friction is a force that strives to counter movement between two surfaces in contact with one another because of unevenness of the surfaces. In some applications, you strive for high friction or grip, while in others you strive for low friction.
The right friction coefficient is necessary to get the optimal clamping force in a joint. The most common application is to ensure that joined materials remain joined. In such cases, you strive for a predictable friction force that enables you to assemble and disassemble components.
With the right friction coefficient, you can also avoid heat production and thermal impact.