Well, in the US, you can't be arrested without probable cause that you've committed a crime. They can't just lock you while they figure out if you've done something wrong, even if only for 48 hours.
If they don't have reasonable suspicion that one HAS committed a crime, supported by evidence, you cannot be arrested.
So while arrests are more punitive here, they are not used to "figure things out."
Of course, if subsequent investigation produces probable cause, they will swear out an arrest warrant and come and get you.
Forgot to add, once arrested, you must be charged within 48 hours or released.
The US Justice system seems to have a rather dubious policy of making being arrested part of the punishment by throwing you in with other criminals and then forcing you to declare the fact that you were arrested to future employers etc even if you haven't been convicted or accepted a caution for anything. That is a bit screwed up if you ask me...