graphics programming - Is there a reason to add options to not use advanced technologies in a game engine?

I have been developing a game engine, and have been discovering and reading up on game technologies such as anisotropic filtering, ambient occlusion, anti-aliasing, etc.

Usually in games, you can toggle these settings on and off. However, if these settings only add nothing but positives, is there a reason to add toggle values for these in a game engine for the developer?

I understand that performance is a major factor, but is there any other reason why these settings are always available to change?