It does seem that most of the earliest webcomics, possibly drawing from newspaper strips, started out humorous. The second generation was inspired by their success (or whatever), and probably stuck to the tried-and-true humor because it
was successful.
I don't know about five or ten years ago, but there seem to be plenty of purely serious and dramatic webcomics now. Maybe you just have to find the right circles and dropdowns?
And of course, a lot of those comics that started out as humorous, even gag-a-day, eventually matured into a mix of comedy and drama, or even straight drama. (I'd post links to other comics, but this is your thread.) I'm not sure how I, personally, feel about the latter. It's harder to take something completely seriously when there will always be some old comedic elements lurking about.
It's nice when a comic can find its footing early, though, as yours has done with choosing a balance between the two. (I
love the hand-done art, lettering and balloons, by the way, but the
occasional blurring hurts my eyes...)
Well, that's my two cents... six cents, tops.
In order to clearly see what is in the shadows, you must first enter them.