If only there was no app stores... sigh... I would only download apps from the reputable company I like (myfavoritebigbank.com), trusting their brand and reputation for my security. If a client-side app can threaten their security, that's a weakness on their part.
And if a lone developer has a cool new idea, and its app is recommended by users I trust on an obscure specialized forum, then I'll decide to install their app from "coollonedeveloper.com".
If only we could invent some kind of "domain names" system that one would have control and responsibility over, instead of trusting some broken unscalable app stores...