What makes Luffy such an attractive personality?

As a manga protagonist he fits the bill of hardworking, honorable and a bit silly but how is he able to disarm the fiercest, no nonsense pirates and killers to root for him.

As Mihawk said in this misquote ‘his power is getting everyone ally with him’ and he has shown time and time again how true this is.

We as readers know that he is not intentionally manipulating anybody and is not interested in leading so what makes people want to follow him?