@PinkFootstool - isn't it more that an arrest can be done to secure compliance? For example, the police cannot just ask for my fingerprints and get them. I can say no or yes.
But if they arrest me then they have a legal power to take them.
So when someone is arrested, it can be taken secure an outcome so the police have the correct legal power to move or gather evidence.
However, the use of the power is to give the arrested individual no choice. Otherwise a person is at liberty to speak or not speak to the police generally: