The simple fact is that there is a high demand for interactive applications. One of the best ways to distribute these applications is the web using JavaScript. If, for some reason, this distribution channel were removed (let's say it was removed by law) the demand would still be there, and the 'older' channel still remains - native apps. If the average person uses, say, 20 webapps heavily and a few hundred glancingly, and let's say that 10% of these survive the transition (probably a high figure) that's still a good handful of new native apps, each of them with their own security issues.