Morgan Meis tries to figure out why people are fascinated by pirates:
There is another aspect to our fascination with pirates. It is existential rather than political. It is about civilization and its limits, about our need for a sense of home versus a need to break those boundaries altogether. The sea has always played a big role in that dialectic. The sea is, potentially, an avenue for intercommunication and exchange among men. It is, in short, a vast shipping lane. But it is also an outer boundary. The land stops at the sea. The city stops at the sea. We human beings have conquered this earth, mostly and swiftly, but the sea is still unnatural territory for us, we aren't as sure on its surfaces as we are on those harder surfaces more suited to bipeds.
The pirate takes that insecurity and runs with it.