Why do we want to be friends with someone?

Friends are important. So important, in fact, that its been proven that friendship can extend life expectancy and lower chances of heart disease. Friendship helps us survive. Friendship ignites the part of the brain that makes us feel good, which makes us want to keep hanging out with our friends.

What is it called when you really want to be friends with someone?

Platonic friendship specifically refers to friendship between two people who could, in theory, feel attracted to each other.