Those pointing out the number of based aircraft which park overnight are missing the point. The 'no div' discussion is not about accepting all diversion requests at all times, regardless of existing business. It is about operating a flexible DYNAMIC diversion policy (as most other airports do). That allows complete discretion to turn away likely nightstoppers, or anything else which is an identified problem, whilst accepting diversions which can be accommodated at quieter times. And there ARE quiet times across the course of the day. Also, the blunt 'no divs' policy by default excludes the likes of executive jets which tend not to impact main apron availability at all. This is why decisions on a case-by-case basis is called for. Not every diversion is a widebody with a crew going out of hours.
Rest assured that those who put the case for a dynamic diversion policy are well aware of overnight apron usage volumes.