Why not? They check hand bags anyway. Even if you don't check everybody it is a huge deterrent to scalpers if the buyer can not be sure that they will be allowe

Why not? They check hand bags anyway. Even if you don't check everybody it is a huge deterrent to scalpers if the buyer can not be sure that they will be allowed in. Imagine paying for expensive tickets, travelling a long distance, paying for a hotel room etc. And then you're not getting in to see the show.