Well, there are two uses of "Sykes-Picot", one defensible, the other not.

The first is to simply use "Sykes-Picot" as a convenient, if inaccurate, short hand for all imperial meddling in the region. The Sykes-Picot treaty was the most infamous example of such meddling, and perhaps the most sweeping in scope. It has also been viewed as being particularly underhanded given that Hussein-McMahon was negotiated just months before.

The second, less generous, but nonetheless incredibly common usage is complete ignorance of how the borders were drawn. I have come across so many references to "the Sykes-Picot borders" that I cannot help but conclude that many of the people who write on the topic for a popular audience, particularly given the flurry of such writing around the Sykes-Picot centenary, simply don't know what they're talking about.