Crazy isn't it. All to keep fans away from shops, bars and restaurants!
It doesn't even work anyway. I was in the area (doing that helter skelter thing with my son) while West Ham were playing Palace. We ended up walking back to Westfield with all the football foot traffic after the match and they weren't letting people in. You end up walking the long way round and I swear the whole shopping centre was rammed with (perfectly normally behaved) football fans within half an hour of the game ending.