The Stranger explores the differences between friendship and companionship. The novel’s apathetic hero seems to draw no distinction between them, or rather, approaches what other characters think of as "friendship" with a detached and indifferent air. He falls into friendships if being friends is easier than being strangers, but would rather remain strangers if that takes less effort than having a conversation. Friendship ends up being something that happens to the main character, rather than something he creates. Of course, one could always argue that this means it isn’t friendship – or even companionship – at all.
Just as Perez and Maman tried to escape death via a blossoming romance, Meursault escapes boredom through his friendship with Raymond.
Meursault uses other people to satisfy his needs. This is actually no different than what other, "normal" characters do in The Stranger – it’s just that Meursault is more willing to admit it. At the end of the day, he’s just like any other person, without the mask of social niceties.