I could equally ask why - since humanity seems to have decided that it, even if not the rest of the natural world, has purpose - that something hasn't already been established.
I don't see that humanity has decided that it has a purpose - certainly not a collective one that's shared by even a majority. Individual humans select a purpose, some of those organise into collectives, but I'm not aware of any of those that are world-wide.
Even if there were, the fact that people have decided on a purpose doesn't imply that the purpose is external - they aren't necessarily 'realising' a purpose imposed on them, but rather generating one for themselves.
Perhaps you could explain what you mean by that wonderfully jargonistic phrase 'emergent properties of the physical'?
Complex arrangements of physical phenomena - say, brain cells - are capable of producing subtle, nuanced behaviours that seem at first blush to exceed the capacity of the components.
Do you have any methodology for deciding that they aren't meaningful?
If you're asking a question that implies a conclusion that hasn't actually been demonstrated, then you're begging the question - in that instance, your question may not be meaningful.
Good try at avoidance. Do you have any evidence that they don't? Note that I have never mentioned unicorns in any of my posts other than in response to posts that already mention them - often within quote markers, so you need to provide the proof of your suggestion.
Except that the question parodies theological questions - you differentiate between 'God' and 'unicorns' for what seem to be entirely arbitrary reasons. You have equal levels of evidence for both, which is just references in old books of questionable provenance, insufficient to the incredible claims made.
So far the attempts to justify treating God as a different category of claim from 'pixies', 'elves', 'brownies', 'dragons', 'unicorns' and other magical creatures haven't succeeded.
O.