People with agendas that include obscuring sources tend to give links, knowing that most folks will be accepting of what they've said and think that a link will back up the assertion that has just been put forth.
Also, folks are lazy or have problems with long connect times to another URL; therefore, if the data is right in front of them, they may actually read it.
As for taking up a lot of screen space with text?
Not to worry for a SMALL pictures uses a LOT more bandwidth that text ever thinks about.