Framing is everything. Lobster was once for poor people, to the point that labor contracts limited how much lobster could be fed to workers. Now it's a delicacy.
Crucially, mushrooms aren't just cheap and efficient to produce, they're actually delicious, so I don't get the association with "poor" people unless one's obsessed with vanity.
Matter of perspective I guess. In the Foundation series the fungal/algae food of the Mycogen district is described as some of the best food the main character has eaten.
