Why is it common to keep separated the bones of the arms from the clavicles?

When I watch tutorials I see always that they keep the arms separated (with “keep offset”), I mean, there is no bone between the arm and the clavicle. Same about legs and butt.
I am a beginner and I see that when I try to rotate an arm manually it can’t rotate if it isn’t connected to another bone, like the clavicle (it just moves). So I suppose that I need to connect the clavicle with the arm to rotate the arm. But in the tutorial they keep them separated. So what is the advantage to keep them separated?

I think that a human arm is connected to the scapular not the clavicle…

Which tutorial are you following, which rig are you using?

Cheers, Clock.

Undependently than what bone is connected in a human arm, in the tutorials I see that the arm is almost always disconnected with “keep offset”.
I am not using anything, I’m just asking why in the tutorials (random tutorials on YouTube) the arms are usually separated and what are the advantages.

“keep offset” is just a way of parenting that does not join the parent and the child together at the same joint. Doing so is more than just a cosmetic choice as it gives more possibilities with bbones (bones that can be subdivided and smoothly bent towards their connected parents and children), otherwise it’s just a question of pivot point and orientation - in a connected relationship, the parent bone always points towards the root (head) of the child bone.