There is a whole universe of possibilities between "hey" and a conversation so good it is otherworldly.
Most of these apps, the user has a profile. If they're not fucking it up, the profile has topics to talk about.
"Hey! Your profile says you love the mets. Do you go to a lot of games? I used to go with my pop, but he just watches the game on TV now" isn't stellar but it's significantly better.
If the other person responds with "Nah [end of communication]" then they're doing a bad job. I'd see that all the time and it drove me crazy.