If you're stringing together a Unix pipe command, TFM might be for, say, awk. Would you rather stop what you're thinking about for 10 minutes and shave that yak, or get a quick answer and move on?
There's another cost to consider: if you do this more than infrequently, learning the tools will save more time than consulting SO repeatedly — particularly if you end up adding and debugging extra steps. Not a big deal for something you're running once but I've seen people running carefully constructed gargantuan shell pipelines multiple times a day because it was "too hard" to learn how to do it all in a single awk / perl step
