oomis 1105 “Oh brother, here we go again. Have couples over, enhance your Shabbos table with orchim….”
Whether or not couples socializing is an inherent problem has a lot to do with the communities they come from. People from more modern backgrounds who are used to socializing with people of the opposite sex (for example, in more modern communities is it very common for two families to share a shabbos meal and shabbos afternoon), will not see a big deal in having couples together for a shabbos meal and in most cases it is perfectly fine.
However, for people coming from more Chareidi backgrounds interacting with another couples is something very new and potentially can lead to problems.
In the back of the new Nefesh HaChaim Rav Chaim Volozhin quotes the gaon as saying that the more gedorim one puts up against arayos the more the yetzer hara burns. This isn’t meant to argue against gedorim c’v, however to recognize a fact of life.
I have lived in both chareidi and modern environments and during those times that I lived in the modern world I thought the chareidim were being so extreme in this a similar areas, however, now that I live amongst chareidim I totally “get it” and understand why for their culture having two couples sharing a meal would be very inappropriate.