This is way more central to why people aren't building on it than you seem to give credit to: people simply can't build on it... I mean, even Bitcoin is programmable (which is how people have been able to build stuff like Lightning and bridges to contract side chains like rsk). Not being programmable--which sadly is kind of a trade-off for their core premise of being "actually private" (not that I am saying that is insurmountable, but it hasn't been solved yet)--means you don't see an ecosystem built on it and thereby no software dependent on it and thereby no "investment" in the platform is really possible. What makes the smart contract platforms potentially interesting is that actually DO SOMETHING problem might be willing to pay for: provide a trustless transactional data store on which you can build other more complex behaviors.