Well, there's a Lego Batman kids comic over here, like the Lego Avengers one, with free minifigs on the front and I bought the first issue for Batman, just cuz I kinda wanted a Batman minifig cuz I love the Lego Batman Movie; they later did Robin II, Flash and Superman and I figured (lol) I wanted a Robin and then that I'd get Flash and Supes. After that, I decided I wanted Supergirl cuz I like her show, Nightwing and the other Bat characters, and Wonder Woman, so I bought the Batgirl LBM minifig split from a set someone was selling on Amazon just to spend some xmas cash, did the same with Batwoman to spend some birthday cash, then last year decided to get Nightwing, Green Arrow, Wonder Woman, Martian Manhunter and Supergirl from eBay.
The Lego Avengers comic started last year and I bought each issue, except #2 which was Venom.
I guess part of it is that they're (generally) a damn sight cheaper than action figures (5 quid for the comic, I paid around the same for the ones I got from eBay, paid more for Batgirl and Batwoman) and they take up far less space. I have them lined up on my desk shelf in front of my 6in Black Widow, my 4.5in Captain Calhoun Trek figure, my 5in Master Chief, my 7in Soap MacTavish, my one Marauder figure and a couple of my AF figures I have on display still.