Probably because you have at least a semi-realistic view of them. Pirates have now been thoroughly neutered for children, which you may not realize if you don't have children of your own right now. Disney has a popular show "Jake and the Neverland Pirates" in which the maximum threat level from the bad pirates is that they might briefly steal your lunch, but only briefly, because you'll have it back by the end of the short episode.
It's like dressing up as a witch for Halloween, you know; there's a lot of horrifying history if you know about it, but if you don't, it's a black cape, a pointy hat, and lots of strained cackling, and little more.
This is why I recommend "Treasure Island" by Robert Louis Stephenson every chance I get. They're all "Walk the plank, me hearties" but they're also blood-thirsty scumbags.
It's like dressing up as a witch for Halloween, you know; there's a lot of horrifying history if you know about it, but if you don't, it's a black cape, a pointy hat, and lots of strained cackling, and little more.