My experience is also that the expectations/style tends to be different when you're dating someone you already know, and dating strangers or near strangers.
If you've known someone for a while in a non romantic way - a friend, a coworkers, a classmate - and you ask them out, you've usually decided you are interested in them based on what you know of them, and if they accept the date, they likely reciprocate that interest. So you're starting from a position of knowing each other and being mutually interested. That's very different than going out with someone you meet on a dating site, club, or alumni event - there, you've got maybe a total of an hour interaction in person (or nothing but email exchanges), and you're starting at a much earlier phase.
For internet dating or meeting people at clubs, there tends to be a very low success rate - for one good match, you go on a lot of dud dates, and there are a lot of people who look good in email, but there's not spark in person (or who aren't that great when you're both sober). So if you're communicating with one person at a time, and have a rate of one date every week or two, you're going to have a pretty low chance of meeting a good match. So a lot of people will communicate with and casually see multiple people. If they know someone is not a match, they stop, and if they meet someone who is a good fit, they taper off the other contacts.
I will say two things about expectations in a relationship.
I do think that after four dates there is zero obligation to work things out, or come to a mutually agreeable solution, or compromise for the sake the relationship. This is the stage where you are figuring out if you are interested and compatible. If it turns out that you're not, you can walk away and try someone else, and neither person is at fault. If you communicate clearly, aren't deliberately hiding things, and speak up when you realize there's an issue, it's not your responsibility if the other person is hurt or angry because you don't have the same system or expectations they do.
The second is that ultimately, if you make assumptions it doesn't really matter what your personal set of rules or expectations are, you can get burned. There's a *huge* range of variations in what people want or expect in relationships or romantic encounters - from extremely conservative to extremely casual, and an equally large variation in what they consider important. If you assume that the other person agrees with your views and act accordingly, and it's something that matters to you, you're setting yourself up for heartbreak, no matter what the issue is.