my projection based on relationships with so/sp is that they find us, sx types, just really inconsistent. we don't put consistency and reciprocity and social contract above our whims, and at times we don't realize the difference between a whim and something that is true for us in a deeper way. sx is measured in urgency, so our sense of time distorts somewhat, and it can be difficult to balance short-term vs long-term. well-developed sp is what combats this (along with the literal skill of time management, using T to mark, measure, and moderate our attention and allow us to truly be aware of what is happening in both a broad and narrow, targeted sense).
i've found many so/sp types have an attraction/aversion to sx. they can both like being taken over by the desires of another, or they can be incredibly rigid in their boundaries and cut themselves off from the desires of others. sometimes oscillating back and forth in the extreme. they can struggle opening themselves up to others desires because they are at times uncomfortable with and somewhat disconnected from their own. they don't feel their own sx counterbalance. this can breed co-dependence.
i know for me, many of my most positive relationships, romantic and platonic, have been with so/sps. especially when they open up to themselves, feel their feelings, listen to their own desires and wait for and ultimately trust their own truth, truly get in touch with their own point of view, all the service they've often practiced becomes a skill through which they can truly give, something not a lot of people really know how to do. that influence has been one of the best things that i have encountered so far.
i think so/sp gets a bad rap. that the development of this path has so much to offer, even if, like all paths, there are some obstacles that people sometimes get stuck on. i think the book "the art of loving" by erich fromm reminds me of so/sp. anyway, it's true that sx sounds more provocative, but it's also often needlessly exhausting, and often quite wasteful. it's great in that it recognizes potential so profoundly, but acceptance and compassion come from a steadiness, a slow consistent process of digesting one's own experience of the relationship point of view, the so perspective, rather than strictly the motivated, active one. the sp provides objectivity and a willingness to let go of yourself to see things more nakedly, more sparsely.