Seriously, is there one? I struggle to find it. However, it is not a frivolous matter: if there is no business case for trustworthy software then there will be no commercial trustworthy software. So, if you know of one, please let me know.
This question of a business case essentially boils down to the nature of the software industry. Is it an industry similar to bridge building, with detailed expectations, stringent norms and personal responsibility, with designers and builders sitting below the bridge during the stress test? Or is it like an insurance industry: selling non-specific promises only to weasel themselves out of any responsibility when you actually need them?
I know that we know the answer: it is like an insurance industry. We all know it. The exception: software companies do not even pretend to promise anything. They do not even pretend to accept any responsibility. It is all clear, black on white, in a 6 point Times, on the bottom of the 13th page of your licence agreement. Did not read it? Your fault.
Software industry is an anomaly among industries, and it will remain such if we do not complain. No software house will ever regret having one user less, but there are many that will regret not having thousands or millions. Money speaks.
Note that my harsh words apply only to the general-computing, game-office-and-network fare of software. There is a large industry of automotive software and dedicated financial software that actually accepts certain responsibility for their products. It is probably because auto-makers and banks actually read licence agreements and actually complain.
What is it that you can do? First: use free open source. Seriously. It is free, it has plenty of functionality and it is not concerned with its business case, because it is free. Actually the majority of the Internet runs on open source. Try for yourself.
Second: reward trustworthiness. I mean: pay for it. If you see a trustworthy paid-for chunk of software do not complain that it is expensive. Do not try to steal (i.e. appropriate) it. If you do so, you destroy trustworthiness.
Third: do not lock yourself in. Do not let others lock you in. If only you can, reject proprietary standards. Which means that if you get disappointed with any bit of software you can move on. Which means that those who want to be trustworthy must keep trying.