Not sure that's always going to be the case - the Lydden rallycross meetings have often clashed with BTCC meetings at Brands Hatch and the Lydden crowd has been very good.
The winter series meetings at Lydden were
cold but great fun with all the dirt flying about and coating the cars, but at winter meetings you certainly would have a smaller crowd as the 'casual' element would be put off by the weather leaving the die hards on the banks huddled round their cuppas.