There could be a variety of reasons for the sliders to act counter to expectations.   Either be ignored altogether or not appear to make a difference.

1) Slider mode - the sliders do not always impact Part volumes.  Their function is dependent on which mode of operation they are taking.  For example, some tone wheel organ Performances default to placing sliders in a mode to adjust element levels instead of Part volumes.   

1a) There are other niche examples such as slider modes under DAW control or some menus that use the sliders as data entry overriding their function.  These "niche" cases wouldn't be present if you were at the HOME screen.

2) Vol/Exp off - there's an option on each Part to turn expression off.  This will effectively disable the slider for that Part

3) Control matrix overrides Part volume - Part volume is a parameter that can be assigned to a source controller (so called Motion Control). This applies an offset to part volume and sometimes that offset can be so large that no matter where you place the slider it will still remain at the same value.  Say your control matrix is currently applying an offset of -127 (negative one hundred and twenty seven).  Then no matter where the slider is the offset would always result in a value of 0.

Please give some examples of factory presets (that we would all have) that have this behavior you're curious about.  I can dissect what's going on in an actual Performance and that may help you in the general case.

This is not an uncommon question and there are probably previous threads that cover all of the cases.