Why do teams demand "Clean Sheets" from CAMs?

The position of the player currently playing in career mode is CAM, but "Clean Sheets" is included in the criteria for achievement when signing the contract.
I think it is wrong to require "Clean Sheets" for an attacking type position.
It is a position that is supposed to help the team win, and that is what they are expected to do.
Isn't it the defensive position that is evaluated by "Clean Sheets"?