According to the current rules:
- Links to external resources are encouraged, but please add context around the link so your fellow users will have some idea what it is and why it’s there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline.
I often see answers that do not contain any reference and even though the content is correct, I think that the use of referenced material is of great value especially for NNLs.
My points are:
NNLs and users in general don't actually know whom they are receiving an answer from, so the presence of accredited reference may help in supporting the content of an answer.
references can help NNLs become acquainted with dictionaries or other accredited sources they may be not familiar with or which they simply don't know how reliable they are.
I agree that the reputation points and the voting system can compensate for the "anonymity" of answers, but many are given by low rep users and, though perfectly correct, they may attract few if any upvotes at times, so I think that the presence of accredited reference would play an important role in giving credibility to answers.
Should, in that respect, the use of referenced material be "always" used when posting an answer?