Doubtless some people avoid using their turn signal for this reason, but it requires thinking. I'd bet that a a more common explanation is based on NONthinking -- simply abject self-centered failure to consider that other people in traffic might benefit from knowing what their intentions are.
Or if they do give it a moment's thought, they reject the notion of communicating with other drivers (except perhaps with the single-finger thingy salute) as unimportant or beneath them. Someone on the newsgroup coined a term for this atbreastude, "MFFY," which explains a great deal about USAmerican public conduct these days, especially in traffic.
The term also explains that "you might get into my lane but you ain't gettin' ahead of me" mentality that leads people to close the gap and prevent your maneuver, should you be so polite as to not only use your turn signals, but use them in announcement rather than commemoration.
Two adjacent MFFY drivers, one each with these respective atbreastudes, can make beautiful music together, at least according to the clangorous listening tastes of the paint-and-body shops.
Turn Signals 3345Dave Head Sounds like the driver ahead of you has his poo together. He decided to change lanes before the last minute (second) and allowed enough time to make his move relatively safely...
Of course, in some situations, you also have the people who demonstrate why "pbuttive aggressive" starts with "pbutt" (not to mention a slightly shorter word), and seem to think that instead of getting into the line of cars headed where they're going, they can zoom up a relatively free-flowing and unoccupied adjacent lane, then pretend it was all a dreadful mistake and would you please let me cut in line at the last moment if I ask real nice. Blocking them out is of course unsafe as well as rude, but the *urge* to do it is understandable.
Then there are the people who seem to think you're just warming up your turn signals for later use. And the ones who interpret them as "last chance to pbutt on this side"...
Turn Signals 3347The fact is, the guy is an incompetent f***. I use my turn signals EVERY time I chage...
--Joe