Why do many sonatinas leave out or greatly shorten the development section?

A sonatina is a shorter and often lighter musical form than the traditional sonata. Because of its condensed nature, the development section—which typically serves to explore and resolve tonal and thematic conflicts—is often either perfunctory or omitted entirely in the first movement of a sonatina.1

While a full-scale sonata movement relies on the development to expand the scope of the work and demonstrate the importance of musical themes, the sonatina focuses primarily on the exposition and recapitulation of musical materials. This structural simplification is common in works intended for pedagogical purposes, such as early piano sonatinas by composers like Muzio Clementi and Friedrich Kuhlau, as well as in specific movements of 18th-century sonatas and opera overtures.12