In a statement published to Facebook on Thursday, the Nürburgring cited safety concerns as the reason for the ban. “The different driving dynamics of two- and four-wheelers pose a risk of misunderstandings—especially for motorcyclists,” the statement reads. “In order to make the driving experience safer for everyone, cars and motorcycles will be strictly separated in the future.”
Any mixed class “racing” adds inherent risk but mixing 2 ton+ metal boxes and 500 pound motorcycles seems like an unnecessary risk.
I still think it should be up to the rider to decide if they want to take that risk, but I can understand not wanting to deal with it as the track runners.