You also make friends with other parents when you have children, especially the first intense childbirth experience, but then also school, sports, scouts, campi

You also make friends with other parents when you have children, especially the first intense childbirth experience, but then also school, sports, scouts, camping, etc. The effect declines as your children get older. After that, I agree, new friendships are rare, but perhaps also unnecessary, depending on your gender and personality (middle-aged autistic males probably have loner superpowers).