As far as I understand it's too inconsistent, i.e. very unevenly distributed within one fruiting body. Not sure if that's the reason, but: if you ever bought mushrooms/truffles in the Netherlands, there is no psylocibin content on the box. And if you try googling, the estimates vary pretty wildly (although it's possible that it's just a lack or proper research)

Also not everyone enjoys the taste of mushrooms or truffles. And psychedelic entities don't care whether they are coming from naturally occurring or synthesized psylocibin ;)

Also, humility and appreciation come in different shapes: for example I recall that Shulgin never consumed his pure psychedelics with juice because he could distinguish 'chemical' tastes and had appreciation for that