Flavour text, world building, or maybe the effect of your artifact counters the normal effect of that artifact.
In all seriousness though, this is a feature I'm considering for the future. But since the entire obelisk will be rebalanced in the future anyway (it's meant to be a mid-late game challenge, not one of the first), I'm not sinking too much time/work into it yet.
In theory, it is entirely possible to complete most, if not all current content without mining the obelisk at all. In reality, that route isn't particularly well balanced at the moment, so mining first is the preferable route.
What I meant was that once there's more content in other directions, the obelisk will likely be made harder than it is, so that you're more strongly encouraged to go other places, find upgrades, then come back to deal with it. But there's not enough content for that yet.
