[uoaei]

On the other hand, arbitrary conjecture in absence of evidence should be treated exactly as such.

It's worth noting that there are a number of phenomena for which we have built detectors to find this mysterious "dark matter", all of which have failed to turn anything up whatsoever. In fact they are less than useless in that we still don't know if any of the proposed mechanisms can even be ruled out yet. The experiments achieved basically zero information gain in that regard.

Occam's razor flashes bright in the cold dark of space.