even putting aside electronic instruments, modern building tools and materials have allowed some acoustic instruments to shrink. check out “mr curly” for an example- a contrabass clarinet that’s a bit shorter if anything than a soprano clarinet, made out of vinyl tubing. another example is the bass ukelele, an instrument smaller than a bass guitar that aproximates the sound of an upright bass thanks to thick rubber strings. in most cases the traditional form of an instrument is preferred just because of familiarity and knowledge passed down from generation to generation, so in order for something to “take off” it needs to address a specific problem, which for most instruments size is not