Why were orchestral works often arranged for piano in the 18th and 19th centuries?

In the 18th and 19th centuries, orchestral and chamber works were frequently arranged for the piano primarily to facilitate study and to allow individuals to enjoy and perform music at home that they had previously heard in a concert setting.1

These arrangements served several practical functions:

• Study and Preparation: Reducing complex orchestral scores to a keyboard version enabled students to learn and practice works without the need for a full orchestra. Similarly, piano reductions of opera and ballet scores were essential tools for the preparation of performances.12
• Accessibility: Because the piano was a central instrument of the era, these transcriptions made large-scale compositions accessible for private performance, bringing the experience of orchestral music into the domestic sphere.1
• Technical Utility: For concertos, reducing the orchestral parts to a keyboard version allowed soloists to rehearse effectively when an orchestra was not available.1

While the term "arrangement" often implies a degree of musical liberty or simplification, these piano versions were vital for disseminating music and deepening the listener's understanding of a work's structure and orchestral effects.213