Why does neoclassical economics assume preferences are fixed and exogenous in nature? Why does neoclassical economics assume preferences are fixed and exogenous in nature? Is this because it's just a convenient assumption to make?

Does this link with the idea of "De Gustibus Non est Disputandum" (tastes are not a matter of dispute), if so, how?

Surely it isn't accurate to say that preferences are fixed when societal influences can easily change the preferences of individuals (e.g. through herd mentality etc.)?
As you suggested in your answer it is precisely this:


  Does this link with the idea of "De Gustibus Non est Disputandum" (tastes are not a matter of dispute), if so, how?


Also in psychology and sociology there is great debate between “nurture and nature”, that is whether really people’s behavior is fully exogenous determined by genes and so forth or endogenous determined by upbringing and society and the debate is still ongoing although both views seem have some merit in.

Second, even though it’s likely that society can affect preferences of the individual it is less clear if economy/economic system or many economic issues studied by economics can so.