How many instruments are there to form the ensembles?

Six or more instruments
In most cases, a larger classical group is referred to as an orchestra of some type or a concert band. A small orchestra with fifteen to thirty members (violins, violas, four cellos, two or three double basses, and several woodwind or brass instruments) is called a chamber orchestra.

Maybe because it was so unique, a form of art, and they could easily store things in it and no one had ever done that before. i’m not sure but that’s what i think : )