I work in ticketing at a large theater. We hold tickets back for a lot of reasons:
- the production wants us to, for production comps, VIP guests, press, photographers, creative team, etc
- they are seats owned by subscribers or are being held to be sold only as subscription seats
- there is going to be rush, lottery, or another discount offer for particular seats
- we expect many large groups to be interested in a particular show
- in times of extremely high demand, box office, the website, and the order by phone system will all have seats they have exclusive access to and seats they do not have access to
- if we expect prices to fluctuate shortly after tickets go onsale
- we hold upper balcony until the cheaper seats in the orchestra have sold well so we don't have an empty orchestra and packed upper balcony
- other reasons i am not privy to