Violin manufacture strives to "replicate the past" because that is where most of the music played with them comes from (on HN I have to point this out!). However, there are plenty of compositions for modern alternatives like electric violins.
Another factor is that violinists haven't run out of ways to express new musical ideas on old instruments. The need to design a new instrument, in order to come up with new music, isn't immediately evident. The modern alternative to the violin, could be a violin in the hands of someone with a modern approach. I'm seeing this happening in contemporary fiddle music, for instance. As a jazz bassist, my instrument is of ancient design, but my playing is driven by ideas that are mostly less than a century old.
Of course inventing new instruments is a welcome avenue of musical exploration. But it's not without tradeoffs. At the very least, the musician will be set back by having to develop new technique and familiarity with the capabilities of a new instrument -- getting your ears, brain, and hands, to work together perfectly in real time. Composers also have to wrap their heads around the capabilities of a new instrument, in order to take an interest in writing for it.
Not to mention alternate fret positioning, partial frets, and things like New Standard Tuning. You still have the same scale, but new shapes change composition.
Violin manufacture strives to "replicate the past" because that is where most of the music played with them comes from (on HN I have to point this out!). However, there are plenty of compositions for modern alternatives like electric violins.