And I care about my writing in a way that I guess I don't care about, say, my bookmarks. If Pinboard went under tomorrow, I'd be annoyed, but that probably wouldn't last. It wouldn't take long for a hypothetical TS shutdown -- breaking links that you hope are built to and within any successful service -- to reach the point of clothes-rending angst.
And that's the extreme case, things coming to a halt. Even TS atrophied and a better tool came along, with my work stuck on thoughtstreams.io, the switching cost is harder.