A stadium that seats seventy thousand for a game sells considerably fewer tickets for a concert. The difference is drawn on the seating chart by the production itself.
The stage design determines the map
Touring productions carry a fixed stage that must fit in every venue on the route, so the chart is built around a structure whose dimensions cannot change.
Everything behind and immediately beside the stage becomes unusable or restricted, which removes a large block of seats from sale in a bowl designed for a central field.
Extensions into the floor — a runway, a secondary platform — improve sightlines for some sections while eliminating floor space that would otherwise hold standing customers.
Production equipment occupies revenue space
Front-of-house mixing positions sit in the audience, typically well back and centered, because that is where the sound must be judged.
Delay towers, follow spot positions, camera platforms and cable runs each claim their own footprint, and none of it can be sold.
The total removed is significant enough that promoters negotiate over it, since every square foot returned to sale is directly worth money.
Sightlines are assessed before tickets are priced
Seats with an obstructed or extreme angle are identified during planning and either withheld, sold with a disclosure, or priced lower to reflect the view.
The assessment is done against the actual rig, including screens and lighting trusses, which block views that would be clear during a sporting event.
Errors here are expensive. Selling a seat that turns out to face a video wall produces refunds and complaints that outlast the show.
Safety and egress rules cap the numbers
Local fire and building codes govern how many people may occupy a floor area and how quickly they must be able to leave.
Standing floor capacity is calculated from those rules rather than from how many people would physically fit, and barriers create further subdivisions.
Pit areas exist partly for this reason, since separating the front section limits crowd density where pressure would otherwise concentrate.
The chart is finalized late and adjusted
Production holds keep a block of seats unsold until the rig is loaded in and sightlines can be verified in the actual building.
Those seats are released once positions are confirmed, which is why good locations sometimes appear shortly before a show with no explanation.
The release is not a promotional tactic but the resolution of an uncertainty that could not be settled until the stage was standing in the room.