Formalities are social conventions used to show other parties that you take a matter, topic, or occasion seriously and that you're willing to follow rules. Usually formalities show up in systems that require trust. You don't want to piss off the other party or make them think you don't have respect for the rules. It has its place.

However, you can afford to be informal about systems that don't require trust. There's no one on the other side to appease. You have to obey the rules to even use Bitcoin so there's no need to show that you will respect the rules. You can't help but follow the rules.