Back on topic from the NHS, how come the football is allowed 25000 at Wembley? Their seems to be less consistency with the spectator numbers than with Premiership refereeing!
Putting my sceptics hat on, I'd suggest it's down to how high profile the relative events are. Much as we'd like to think otherwise, the Prem Final just isn't as big a deal in the national non-sport press & public psyche as the Euros, Wimbledon or Ascot. Because of that, the people making the decisions want to put across the idea that they're opening things up without actually doing too much about it are picking pilot events based on the PR impact that the stories will have. By showing photos in the newspapers/on TV of bigger crowds at Wembley, in Centre Court or on the trackside at the races makes a bigger story than the crowds at Twickenham for the final.
Football, Wimbledon, Ascot etc are more firmly ingrained into the national identity as events than the Premiership final is. When you want to to set a narrative of "Look! We're opening nice things for you!" while actually wanting to keep things locked down relatively tight generally, having crowds at Wembley etc hit home harder than crowds at the Rugby. It's a different matter when it comes to the 6 Nations. That's an event that has sufficient "draw" to the disinterested viewer to rival football, tennis, racing, etc. I reckon if we were playing the 6 Nations now, they'd let *that* be a pilot event.