I really dont know if I want to say that there is a meaningful difference between the various disciplines within the social sciences. I think most disciplines partly overlap each other many times ( they refer to common theorists, and sometimes each others theorists/researchers).
I also believe that many splits between disciplines depends on prestige, pride, prejudice and ignorance. I can even hear lecturers and professors express themselves negatively about other disciplines. This in turn affects students who are not familiar with the other discipline, and therefore can not see through the lecturers and professors prejudice.
What once is disciplines that parted ways, seems to be increasingly come back together.
This cooperation between disciplines can definitely be just a trend that will persist for decades. But I guess they sooner or later will part again, partly to create a clear understanding of the different social phenomens they are studying, but I also think there are a lot of prestige and interests from their own ranks to position themselves alongside other disciplines .
Today I also seem to see a boom in cross-disciplinary programs at universities in Sweden . However, it is something that I personally am not sure whether it will dilute the public trust of the scientific disciplines and academic education – it gets too theoretical.
To summarize this
I think that:
1) If I'm supposed to see a meaning with the differences between disciplines, it is to create space and opportunities for a discipline to elaborate themselves in their own scientific methods. To evolve without being disturbed by other disciplines.
2 ) While I see a futility in holding on to differences because a lot of scientific knowledge is lost in prestige struggles and mudslinging going on between different disciplines.