The difference is precisely what you mentioned, people there expect to have dates and find a partner. There could be other people trying to get something else (heck there are even scammers) but it's not your expectation to start a convo expecting to get somewhere, it's the goal of the app. This doesn't happen in real life, in fact, if you try the same approach, you'll be seen as creepy depending on the context. Dating apps should skip this initial uncertainty and technically make it easier to get to the point.