Infographics attract visual learners—which is what most of us are. And that's one big reason infographics are an ideal medium to use in digital marketing: They're more apt than solely text-based content to attract website visitors.
Done well, infographics can present ideas, data, and other information into a single piece of content that's relatively easier to digest.
Blogs and other online publications (like the one you're reading now) happily republish infographics created by marketers and others—because, again, infographics attract readers. Moreover, those readers/viewers are also more likely to share infographics on social networks and their own blogs.
Those are wins—in the form of backlinks, brand awareness, and website visitors—both for creators of infographics and for those who (re)publish them.