You can pretty much look at any "big" series here. You'll see thousands of subscribers. Logically, these are not all the same subscribers to every other series with thousands of subscribers; there may be some shared, but the vast majority will be different. Considering how many registered users exist for Tapastic, it would be extremely unlikely that all, or even the majority, would be creators.
There is comparatively a handful of messages here at the forums in the course of any day, and they tend to be in large part the same groups of people. The forums are where primarily creators go to discuss, so it may seem that there are more creators than readers -- that is an illusion. The forums are more typically used by creators, so that's why there sometimes appear to be more of them, mainly because they're vocal and noticeable here.
It's also worth looking at, say, the likes on pages. Certainly, some of the likes might be from creator friends, collaborators, or such, but most of them are from people who are reading the page and enjoying it.
Last but not least, you can read through the subscriber list. Most of them will not be creator profiles.
Honestly, it makes me wonder how casual people think creating a comic is. It's really quite a lot of work, and most people in the world can't stick with it. In fact, most people don't even try. It's not just something for anyone and everyone, as much as I encourage people to find their creative expression. It's a lot more involved than, say, writing a fanfic. But even in the textual medium: just because someone wrote a fanfic once doesn't mean they have the dedication to write a novel, or even a formal short story. Most certainly will not have the dedication to do serial installments of an ongoing tale.
The long and short of it is this: there are, beyond any doubt, more users who are just readers than users who are creators. There simply are not that many willing or able creators in the world, much less in webcomics, much less on this site.
