Function vs fashion or whats "in" or hip at the time.
Ned Steinberger is/was a visionary, same as Leo in his time. The headless tuning system, composite construction, use of active electronics, minimalist approach to shape. These are all things he used at once in one instrument. Typically people shunned it, not because it was without merit, it just wasn't widely used then.
Yes in the 90's the trend of "vintage" took focus off the "Steinberger" styled instruments. When you look at the XL2, L2 bass, it will be played by people continuously into the future, Why? because it was designed to be an exceptional bass. It wasn't made by a marketing group to garner a market share, it was made by an insightful engineer/artist to try and over come short comings in previous designs.
Those that play off the design because they once picked up a Cort/Arbor knock off and didn't like it, is ignorance when compared to a XL2 or L2 model.
Technology in the last 10yrs has allowed so many raw ideas to become feasible and mainstream. The old thoughts of graphite being brittle and sterile, clearly have never played a all graphite Status bass. My Stealth II has warmer sounds than my P-bass with Qrt pounders. Ask any musician that uses graphite necked or full instruments in a live setting and they all will tell you how stable they are. Its why the Ox had Status build his Buzzard out of Carbon fiber, and why FOH asked Flea to put down his vintage Jazz and start playing the Modulus live. Lee Sklar said during the Phil Collins whole tour, that he thought he only tuned his L2 twice.
No single bass design is going to make all players happy, same with any tech development is going to be embraced by all players.
But to deny them because of "personal" opinion or lack of understanding, then your handicapping yourself to evolve and grow as a player and person.
So to the OP, Yes there have been developments, just people choose not to see it or embrace them. Maybe it's fear, Maybe it's ignorance?????
I just say it ALL GOOD, and I'll try anything at least once, just to try and expand my understandings.