Great question! I've been working towards self sustainability for years and the switch of the staples is probably the hardest. Staples are a few crops that store well so you can use them whenever, and they are grown in enough quantity to meet your caloric intake and have small enough negative constituents that you can eat tons without huge side affects.
In my ideal there wouldn't be 5 "staples", but instead much more variety. Pecans for pie crust, squash spiralized for noodles (squash is ab annual, but here it grows in trees and just about every where you let it), and a diet that doesn't rely on staples. That probably means rethinking your way of cooking. Pumpkin pie may be more or less the same, but you might rely more on trail mix for snack rather than pretzels or potato chips. You might eat a smoothie for breakfast rather than a slice of toast, etc.
As for why else you might not be eating them: they aren't as heavily subsidized here in the U.S. so their upfront cost to consumers is more. Almond flour is significantly more expensive than wheat flour, though I can't imagine it taking significantly more effort to make it. It will also go bad faster since it has a higher fat and protein content.
Here I am working on making acorns easy. We eat a lot of winter squash- stuffed pumpkin, pie pumpkin, spiralized pumpkin, soup pumpkin, stew, stir fry, etc, and I am awaiting patiently for my fruit anf nut trees to produce better. I also harvest maple seeds, which are a nice crunch bit to add to salad. However, there's no staple crop because I plant such a variety.