Look at it from a viewpoint of tiers to visualize it better. Pretend that each tier contains all the sub tiers below it.
The one at the top contains all tiers, but not itself, because the top tier has no original content to contribute.
A set of all sets does not contain itself, because it has no substance to contribute. You could argue that it does, saying you’re adding the zero of it’s non-material, but the end result doesn’t change regardless.
So, in the end, it’s just irrelevant.