They don’t; so make web pages scannable
Here’s the title of one of usability expert Jakob Nielsen’s earliest articles on writing for the web[1]:
“How Users Read on the Web”
The first paragraph:
scannable
Why write email that’s easy to skim?
Because only 19% of e-zines get read thoroughly
Email newsletter subscribers skim 69% of the e-zines they receive, according to the Nielsen Norman Group’s latest eyetracking study.… Read the full article