That's actually what I assumed I would use it for, and I'm not sure why I didn't. Now I find I'm spending huge amounts on (e.g.) the Howard the Duck Omnibus when I could easily have read every issue during my free six-month trial. I could easily have read an Omnibus worth every month during that trial -- £600 of comics, absolutely free. But I didn't.
And it's not really a paper/screen thing -- yes, I prefer paper to read off, but I didn't mind the screen experience. I certainly don't hate the screen so much that £600 is a sensible price to replace it with paper
So it honestly comes down to accessibility. Crazy as it sounds, paper is more accessible than on-line... no, that's the wrong word, not accessible, noticeable. I had six omnibuses on my tablet but I didn't notice them. They're invisible, with nothing to prod them into the forefront of my mind. But as I sit here now, I can see the Howard the Duck Omnibus and feel the anticipation of when I finish my current book and can start it. It's in my mind every day, advertising itself... yes, you're going to so enjoy reading meeee....
That's something that on-line comics can't do. At least for me ... maybe people more attuned to the technology think differently.
(It's exactly the same for music. I have a number of downloads that have been sitting unheard for ages. Because how can I remember them when I've got a stack of new CDs in line of sight, asking me to play them?)