Because there are a lot of scientific wackos that are trying to push it to mainstream without any proof, see e.g. PhDs in congnitive neuroscience with focus on art and whole conferences organized around such ideas. It looks like some New Age cult inside science. Whether it's true or not, there is no methodology how to measure it, putting it outside scientific domain. It's on the level of simulation hypothesis. The rationale is that consciousness as a quality exists and is present in universe, so there must be some mechanisms for consciousness to emerge - if it is another layer or whatever on top of universe we have no clue. But most proponents of the theory sound like cultists.