I feel old seeing to many variations on egg volumes. When I was a boy the tray had 36 and you could fill a half dozen carton or two hals dozens stuck together.
They stack better than boxes, so it makes sense to transport them that
way for restaurants and other kitchens.
I haven't seen the 30 trays in retail stores in several years. I guess most people don't need 30 eggs at a time or it's difficult to transport unwrapped