I figured if Guybrush didn't know anything, then the player wouldn't be frustrated when they didn't know how to do basic pirate tasks. Which was the whole genesis for the opening line:

"Hi, my name is Guybrush Threepwood and I want to be a pirate"

It told the player that Guybrush didn't know any more then they did, and they were going to learn together.

The recently played Hitman had this problem. I am supposed to be this kick-ass hitman - Agent 47 - who is, as stated on the box: "brutally efficient". But I wasn't. I sucked. And badly.

Not that I'm recommending that Hitman starts out with:

"Hi, my name is Agent 47 and I want to be a hitman"