I would go even further to suggest that some scientists find the fact that they are not required to publish their methods and data openly convenient, as they avoid scrutiny that might falsify their claims. Bloomberg has an interesting article: http://www.bloomberg.com/news/2012-01-10/scientists-share-se...

Regarding incentives: incentives are created, it's not like the current status quo is not based on incentives, researchers seek prestige journals because they want to get funding, and in effect public funding bodies enable these incentives by inaction.