They could do that but then they'd probably have to charge you for it.
By spreading the article across several pages, the content providers are able to display more ads as well as rack up more clicks (which in turn attracts advertisers).
That's why so many websites have those somewhat annoying "Top 10" lists that force you to click through page after page to see everything.
I don't complain too much about this practice because it allows me to see the content for free, as advertisers are supporting the website. It's like broadcast television. You either put up with the ads to see the shows for free or you subscribe to Netflix or HBO and pay the fee to avoid the ads.
A determined person could install ad-blockers on their browsers and avoid most of the ads. However, most people don't bother taking the trouble to do that. This is what the websites count upon.
Very similar to the business model for broadcast radio and TV. People can easily DVR their programs and then skip ahead through the commercials, but most people don't bother.