Read this article by my colleague Corinna da Fonseca-Wollheim. It’s long past time someone looked at the concert-going experience in classical music from the practical standpoint of what people do during the downtime (this avoids the endless, fruitless theoretical debates over marketing to new audiences).
I could do without intermissions myself, shorter programs are ideal. Of course, some operas are long, but none require massive scenery changes. The length of productions at the Metropolitan Opera is a product of the need to fill a too-big space that has, relatively, too much money to spend. Many of Verdi’s greatest operas, like Rigoletto and Falstaff, have a compact duration and could be done without interruption.
The story of how concert programs and etiquette developed is a long and complicated mix of the rise of the bourgeoisie, the idea of the professional and, in the 20th century, artist management: conductors and soloists fly around the world, appearing in concerts designed for their remuneration. There is no need to have an overture, a concerto, then a symphony on every orchestra program. It’s as tired a formulas the head-solos-head jazz ‘arrangement.’ More like this, which was done without intermission and was meant just to convey great music.