It's because the only innovations that "count" in the mainstream marketplace are the ones that take us from "not good enough" to "good enough", not those that take us from "good enough" to "excellent". In other words - as a startup, you get customers by taking a non-consumer and turning them into a consumer. It's very hard to take a consumer and turn them into a consumer of something else.

In the 70s we went from "not good enough" to "good enough" in price, but once we got to the PC clone wars of the mid-80s it was hard to go much lower. Then in the 80s and early 90s we went from "not good enough" to "good enough" in user experience, with MacOS 7 and Win 95. The 90s OSes were all attempting to take a "good enough" user experience and make it excellent, and that's where they failed - most mainstream consumers don't care enough about excellence to make it worth learning a new OS. Instead the late 90s and early 00s took us from "not good enough" to "good enough" in information, with a big cost in user experience. The web sucked as a UI and still does, but it opened up literally billions of sites worth of content that a desktop user could only dream about. Now the web has created this whole new problem of trust, which cryptocurrencies solve, but at the cost of regressing 30 years in performance and usability.