Because they don’t want to accept that their sibling or child or relative could possibly have these issues. Like it’s a stain on their genetics. And if they don’t have those issues they won’t even begin to comprehend what you’re going through. It’s really hard when you don’t have that family support. Stay strong and surround your self with people who do care. And if you have crippling social anxiety we are here. Therapy will help tremendously with coping mechanisms to get your self out there meeting new people.