‘Be concise’ is one of the most common pieces of advice given to writers.
Cut out the fluff. Get to the point. Keep it simple, stupid.
It’s kind of reassuring, because it turns editing into a binary, almost mechanical task. Pull out the weeds and leave the flowers. Eliminate the unnecessary, and what remains must be OK.
But what is an ‘unnecessary’ word?
For simple, factual writing, that question is fairly easy to answer. A message like ‘Mind the Gap’ cannot be improved by adding words, nor by removing them.
Certainly, you should avoid fancy phrases that don’t add any value. But words do much more than just tell.
For example, if you want readers to remember your message, it helps to repeat it – not mechanically, but artfully, so they can see your point from a few angles.
Or, if your reader is new to a topic, you need to pace their learning, or offer them some reassurance. Writing ‘all facts, all the time’ could be so cold and confrontational that they simply stop reading.
Finally, if you want the reader to change their mind or take a certain action, you need to empower them to make a different choice. That process takes time; a simple call to action may not be enough.
To sum up: only use the words you need – but be aware of all the reasons you might need them.
Read more about clear writing in How to Write Clearly.