There are multiple ways of asking another person to engage in an action. Many people don't reflect about the different kinds of asks, use the asks that their cultural conditioning dictates and don't get what they want. They might stay silent because they don't want to inconvenience the other person with a strong ask. Other times they express a strong ask and inconvenience the other person more than they desire.
Invitations, requests, demands and commands
This post explores the differences between invitations, requests, demands and commands. While sometimes people say "I request you to take out the trash" when they mean "I demand that you take out the trash" it's still useful to mentally distinguish the different kinds of asks.
An invitation is about giving another person an option to do something. If I'm holding a party and have a guest list, an invitation is a requirement to attend the party but I'm completely okay with people who would be welcome at the party not arriving. If the other person thinks they have a better option then the option that my invitation gives them, I'm not expecting them to follow my invitation.
A step above an invitation is a request. When I'm sitting in a room with high CO2 I might request that another person opens the window. If the person follows my request they are doing me a favor that I appreciate. If they however don't open the window that's also fine with me.
A step above a request is a demand. If I want to read a book that I lend a friend again, I might demand that my friend give me back the book the next time we meet. If the other person doesn't bring the book the next time we meet and doesn't have a good reason, I'm going to be a bit angry at them not fulfilling my demand.
A step above a demand is a command. If I'm in court the judge gives me a command to tell the truth. The command implies that there's a punishment when I violate it, even if I can present a reason for why I don't think it was a good idea to tell the truth.
In the Ask and Guess culture distinction there's the idea that a culture either does their asks with invitations and requests or does the asks with demands and commands. In practice, people who are in a guess culture environment will often interpret the invitations and requests as demands. It requires cultural norms that allow invitation and requests to be made without being interpreted as demands.
On the other hand, it's a failure condition in cultures that focus on making asks via invitations and requests that people who make demands do it in the language of requests and get angry when their requests aren't fulfilled.
In English the word should is linked towards demands while must is linked to commands. Nonviolent-Communication labels demands as violent and proposes to get rid of demands in social interactions. While I do consider it generally valuable to use invitations and requests for interpersonal interactions there are cases where demands are appropriate.
In our Western world commands have little place in interpersonal interactions outside of organizations like the military that need to be able to get soldiers to follow commands reliably.
Instead of following a rule of never using demands, I propose that the wise thing is to strive to use the ask that's best in a social context.