I think it may also have to do with people's perception on family.
An out-of-context picture featuring a father and a daughter tend to get "aww, so cute" feeling from general public.
Also the fan culture kinda shapes all kinds of misunderstanding of the character through influencial fan artists and bloggers.
An artist who draws cute Magnus family pics may well understand the actual relationship they have in comics, but the casual viewers only see a cute fan art and their brain is already shoving all kinds of loving family tropes on them. (Reflected by the comments.)
By comparison, Wanda with Avengers or even with Vision won't be considered cute enough for casual viewers.
Can you believe there are people who pitch something like "Wanda gets the father she always wanted." I wonder where that came from.