Why did Bach write a large amount of music?

Bach wrote a large amount of music largely because he was hired to do so. Throughout his career, he held various positions that required him to produce music for specific occasions, such as church services, court functions, and other public performances. For instance, as a church organist and later as a cantor at St. Thomas Church in Leipzig, he was tasked with composing new works regularly for worship services, which contributed to his extensive catalog of sacred music. This professional obligation not only motivated his prolific output but also guided the styles and forms he employed, reflecting the expectations of his patrons and the needs of the community he served.

While inspiration from religious devotion certainly played a role in his music—considering the significant amount of sacred music he composed—the primary reason for his extensive body of work was his professional engagements. Bach's music was often a response to specific job responsibilities rather than just personal enjoyment or competition with other composers.