Why is it so hard for people to just be a genuine friend? Why when someone messages you, 9 times out of 10 there's an adult ulterior motive behind it?

Genuine friendships I've found tend to grow from shared experience, common interests, time spent together. A natural sort of feeling versus a message that is a more targeted sort of vibe. Not saying messages are bad, just that I'm not expecting a genuine friend to show up in my dm's. Would be nice to be proven wrong someday.