Because it's an opinion formed on actual knowledge rather than media reports...
Not saying that X-47 isn't a fantastic technology demonstrator and a clear indicator of the future, but it's a long way off where the overall F-35 programme currently is. The difference between being an X jet and being an F jet has allowed X-47 to solve issues encountered quickly and the fact that the programme managed to get funding to continue is testament to a lot of hard work and recognition of its potential.