First person pronoun overuse is the most immediate symptom of low social intelligence. This becomes clear in a way you could never otherwise imagine once raising children with certain forms of autism.
Not all autistic people do this. It is just one symptom among many in a big mixed bag called a spectrum.
Over use of first-person pronouns occurs because a person struggles to extrapolate outward from themselves and their speech reflects the center of their thinking, which is just themselves. Low social intelligence describes the inability to relate to other people in a normal capacity. Not everybody is excellent at empathy, but for people with low social intelligence its a massive gap.
It is such a gap that many people who suffer from extremely low social intelligence realize its a gap because they eventually figure out other people don't want to be around them and they don't have the social relationships they see other people casually having.