I think the amount of contact has gone up since the new full rear bumper rule came into play. Less consequences = more contact. If you increase the chances that contact will end your race just as much as the person you are planning to shove out of the way then there will be less contact. IMO
It is also a matter of experience, respect and race craft. You generally see good respectful racing towards the front of the field and the further back you go the uglier it gets. It’s generally the local/regional level racers trying to make their way into the national level scene and are probably used to this kind of racing at their local level.
Or they drive like a European and think that swerving at you on the straightaway is acceptable. :/
If you make it towards the front of the pack and drive like an a-hole, chances are you will be dealt with like an a-hole. Once you learn this lesson, you tend to make smarter decisions.