They don’t. People rarely read Web pages word by word; instead, they scan the page, picking out individual words and sentences.
This is a big rule in the web that people just don’t read. You can see it in internet discussions where people get angry over headlines and proudly proclaim that “they ain’t reading all that”. Any attempt to get people to read, like Twitter’s prompt, get’s people complaining.
People will never read so it’s better to make copy scannable as well as find a way to consolidate the major points, leaving the body for those who really want to learn.