Those comics do that huge gutter thing for one or both of these reasons:
1) a lot of people complain when their updates are "short," so they make it seem longer by adding more empty space.
2) They want their comic to be viewed on the phone, and they want the one panel per screen effect. The correct way to do this is to code your page to force that effect, but not everyone knows how to do it (and not everyone is ABLE to do it even if they know how to code, e.g. when uploading their comic to a platform like Webtoons)... So it's a less than ideal workaround.
Big gutters can be used to indicate things like passage of time. But when you see them everywhere, chances are it's either 1) or 2) or both.
