I know that this forum should not replace a good bibliographic research, but... It is quite useful to know which book or paper or tutorial or any other external source of information that people have in mind when they explain advanced physical concepts.
Moreover, having quickly a common background on a topic by giving explicit references may facilitate further constructive discussion or avoid "(apparently) stupid questions".
Contrary to others opinion, I think that giving explicit references and sources may help students to develop their autonomy. It gives them the example of what is a good source of information, incite them to read and show them the importance of references in research. It is always a good thing to enhance this culture, even among experienced researchers.
Thus, I think that Physics stack should promote explicit source citing. Users should be rewarded for giving explicit references and other should be able to vote for the pertinence of the given sources.