I'm building a world where kaiju-sized creatures exist alongside regular-sized creatures. How these kaiju don't crumble under their own weight doesn't matter, and can be explained away by them being biologically separate from the regular creatures and not made of what everything else is made of. Aside from that, they're basically giant organisms that live, consume, reproduce, and die.
The thing is, these kaiju are a late addition to my story, and the story could work perfectly well without them. The setting originally is a low fantasy medieval world where various fantastic megafauna coexist with people. However, these kaiju fit the themes of the story and make the story feel more fantastic. And I just like seeing them in the background, or at least the marks they leave behind, like giant footprints and skeletons (the story is for a comic by the way, and seeing gigantic versions of normal things is always cool).
My question is, what should I pay attention to regarding these kaiju so I can arrange them to not change the world in a significant way, at least until I want them to?
Some problems and possible explanations I have thought of:
How are they not destroying settlements all the time? They're big and slow, so they're easy to spot and avoid. Also, maybe they move in predictable pattern and avoid certain areas, so that's where civilizations grow.
If they are made of super strong exotic materials, why are people not using it to make stuff? Maybe the hard parts like the bones are so hard that people can't do anything with them with the current technology. The less hard parts like flesh and blood might be toxic or dangerous in other ways to regular life that people wouldn't want to touch them.
Why are these kaiju not what everyone in the story is talking about? Maybe they're rare enough or live far enough away from civilization that they're not a concern for most of the time. Like solar eclipses or hurricanes, people don't talk about them until it's immediately relevant, like when they're coming near a settlement or when people have to move through their territory.
Anything else I should think about?