While I get your point, zkSNARKS preceded blockchain by two decades.
The ZK proof protocols being used today in blockchains are very different than those envisioned in the 80s. Specifically they are "non interactive" and "succinct" (proof is very short and easy to verify). Most of the massive leaps in development of ZK proof technology recently has been led by crypto currency space.
That being said, zcash is a quite useful construction.