Wider seats for bigger bottoms
In an article for The Guardian on Dallas' new Winspear Opera House, Ed Pilkington notes that the theater seats just 2,300, compared with 3,300 at the city's old opera house. One motivator was to enhance the intimacy of performances. Another, more practical, reason: "People want wider seats, as basically they have bigger bottoms," says architect Spencer de Grey:
http://www.guardian.co.uk/artanddesign/2009/oct/14/foster-winspear-opera-house-opens
Creating more leg room, especially in the upper balconies, was a priority in the renovation of the old Carpenter Center into Richmond CenterStage's Carpenter Theatre. Providing that leg room, and adding aisles, reduced the theater's capacity by about 250 seats, to 1,750.