The designers seemed to have expected backgrounds to play some role in establishing some features for the immediate setting. For example the noble background has an extensive list of questions and player and DM should talk through before the campaign begins:
It's not impossible to establish these details in the middle of play (as mentioned I did so with my one noble character), but it might require retcons or changes to the fiction that contradict previously established truths. If the table goes through a session 0 where everyone goes through and answers all these questions, I would expect the experience in play to be more fluid. I've never encountered a "mother may I" situation with backgrounds with three different DMs.
On that note, the emphasis on rulings is an acknowledgement that the rules can't account for every instance of fictional positioning, so for expediency the DM is tasked with adjudicating the situation like a referee and making a ruling. Specific beats general. With regards to backgrounds, they speak to a general, context-less situation. If the questions listed in the Backgrounds section haven't been answered ahead of time, the DM would be tasked with looking at the fictional context and making a ruling.
Let's say a noble elf character wants to visit not only another noble, but a close friend in a nearby dwarven mountain. They can secure an audience, right? The text is very clear? But maybe the dwarf character is mad at the elf, unbeknownst to the latter. Or maybe the dwarves are doing something secret and want to keep all outsiders away. The specific fictional context beats the general rules text.
Work with your DM to come up with an appropriate title and determine how much authority that title carries. A noble title doesn't stand on its own-it's connected to an entire family, and whatever title you hold, you will pass it down to your own children. Not only do you need to determine your noble title, but you should also work with the DM to describe your family and their influence on you.
Is your family old and established, or was your title only recently bestowed? How much influence do they wield, and over what area? What kind of reputation does your family have among the other aristocrats of the region? How do the common people regard them?
What's your position in the family? Are you the heir to the head of the family? Have you already inherited the title? How do you feel about that responsibility? Or are you so far down the line of inheritance that no one cares what you do, as long as you don't embarrass the family? How does the head of your family feel about your adventuring career? Are you in your family's good graces, or shunned by the rest of your family?
Does your family have a coat of arms? An insignia you might wear on a signet ring? Particular colors you wear all the time? An animal you regard as a symbol of your line or even a spiritual member of the family?
These details help establish your family and your title as features of the world of the campaign.
Choosing a background provides you with important story cues about your character's identity. The most important question to ask about your background is what changed? Why did you stop doing whatever your background describes and start adventuring? Where
did you get the money to purchase your starting gear, or, if you come from a wealthy background, why don't you have more money? How did you learn the skills of your class? What sets you apart from ordinary people who share your background?
It's not impossible to establish these details in the middle of play (as mentioned I did so with my one noble character), but it might require retcons or changes to the fiction that contradict previously established truths. If the table goes through a session 0 where everyone goes through and answers all these questions, I would expect the experience in play to be more fluid. I've never encountered a "mother may I" situation with backgrounds with three different DMs.
On that note, the emphasis on rulings is an acknowledgement that the rules can't account for every instance of fictional positioning, so for expediency the DM is tasked with adjudicating the situation like a referee and making a ruling. Specific beats general. With regards to backgrounds, they speak to a general, context-less situation. If the questions listed in the Backgrounds section haven't been answered ahead of time, the DM would be tasked with looking at the fictional context and making a ruling.
Let's say a noble elf character wants to visit not only another noble, but a close friend in a nearby dwarven mountain. They can secure an audience, right? The text is very clear? But maybe the dwarf character is mad at the elf, unbeknownst to the latter. Or maybe the dwarves are doing something secret and want to keep all outsiders away. The specific fictional context beats the general rules text.