Punctuation is a tool to bring a sense of pace to the reader’s experience.
An invitation to pause and reflect, without demanding a halt.
An invitation to move forward, to gather speed, to accumulate an understanding as an idea is being expressed.
As written communication is more and more composed on screens for instant transmission the dash is being used more frequently.
Its use is a product of the speed of composition; an indication that there is no time to consider the length of pause that readers are invited to make.
The reader must determine whether they are being introduced to a new thought; considering two interrelated thoughts; pausing to reflect before continuing the same thought; all for themselves. If the speed with which these missives are read allows for any such reflection at all.
In Semicolon, Cecelia Watson observes:
But the dash nowadays is the Punctuation Mark of First Resort, able to take the place of commas, colons, semicolons, and full stops. We now live in the Era of the Dash. Dashes are dashed off right and left by millions of thumbs sweeping fleetly across millions of mobile phones.
The dash is so easy, so quick, and – when deployed in the way it often is now – so conveniently empty of meaning.