Why are some panels just sketches? I have been reading some Boku no Hero Academia and in some chapters (only very few) there have been panels, which looked like sketches and not like the rest of the manga. Since it were only single panels, I didn't think much of it. But while reading chapter 182, there have been whole pages like that (s. picture below). 

Did the artists run out of time and so, they weren't able to complete all pages? Or is there a different reason for this?


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Thanks to the explanations in the comments.

As expected, the "unfinished" look is most likely caused by a lack of time on the side of the artists.

I am surprised to hear, that it seems common enough.