Actually, boxing is primarily an anaerobic sport.
The fighters I primarily deal with are amateurs, their bouts last four 2:00 minute rounds. Before I started working with them they'd typically jog 2-3 miles as requested by their trainer. Excluding warm up I'll have them do something like four 400m sprints with a minute between each, three 200m sprints with 30 seconds rest between sprints, and one 100m sprint. I've noticed improvements in their stamina and an improved focus since the shorter distance combined with a rest period tends to make them feel like they're doing less work.
I've been involved in boxing for nearly 12 years and messing with S&C programs for five years, this isn't stuff I've read in Sports Illustrated. Boxing is just an inner city sport who's S&C is slowly coming out of the dark ages. Fighters just jog 5 miles because Jack Dempsey did it, then Joe Louis, and so on. To this day most fighters will probably rely entirely on jogging long distances at a slow pace for their cardio for no other reason than another fighter did it.