I think the practical difficulty for ROs might be more to do with not being able to be confident that they will have sufficient marshals/helpers available. And some registration venues might not want a bunch of sweaty runners coming in and out. The circuit training class I attend takes place in the local primary school - I'm not sure if its going ahead or if they want us to play outside for the time being. I'm sure the majority of us as runners would be happy to turn up at races regardless and carry on more or less as normal. Must be safer running around the hills than being in an office/pub/cinema/supermarket.