This, as we all know too damned well, is because Elly is a brittle, angry jerk who assumes that her children despise her and don't want her to ever enjoy life or have a public identity. In her mind, they want to erase her from the picture and keep her in the background and never, ever acknowledge her contribution to their lives. The reason for this paranoid dread of being consigned to mute anonymity seems to me to be her projecting her own desire to crush everyone under her feet onto the blank canvas of children who see her as a domineering monster who spends each day figuring out new ways to blight the lives of the children she only gave birth to so she could have someone to tyrannize.
This would be bad enough were it not combined with something else that makes her a pain in the ass: her default belief that anything that she can't understand is clearly part of a plot to destroy her. As I've said before, she clearly expects her children to say "You know what, Mom? I really am a selfish little brat who sponges off of you and Dad because I'm evil and love chaos and should thus atone for my hateful parasitism!" and when they don't, the wholly unexpected event leaves her as baffled and horrified as their not taking life as pointlessly seriously as she does.
The end result of this is that she's blighted the world with two fragile idiots who also don't understand children and lose their shit when they don't say things they're supposed to. You would think that a child who used to try to have as much fun as she could wouldn't freak out like a maniac because she thought that the made-up word "stousins" was part of a plot to eat her brain but after about a quarter of a century of life where a kid can't be a kid, it makes sense that Liz grew up totally unable to relate to children as anything other than an antagonist to fight with.