"COMINT" provided a look at how both Soviet and American spies and assets acquire information and the sacrifices that are made to get a step ahead of their adversaries. Often, it involves sex.
In order to get information out of a target or asset, it's necessary to create a relationship built on trust. When there isn't time to make that deep connection, the next best option is intimacy.
Elizabeth and Philip have perfected the use of both methods during their years working for the KGB in America. In a short period of time, we have seen both spouses seduce targets and assets for information, though it seems that Elizabeth uses that tool more often.