You extol the fact that many apps available for iOS are also available to Android and I won't disagree with that. However, when apps by the same name and from the same author are placed side-by-side the iOS version is reported by most reviewers as feeling more 'complete' or 'finished'; in other words, more attention to detail in the iOS version. So yes, downloaded apps are a factor.
Web apps, on the other hand, are less of one. Sure, any browser can access web apps and they can do many if not most of the same tasks, but now your network overhead is massively increased--especially when you're using the device remotely and have limited, if any, network access. This is where the downloaded app especially shines.
Virtualized desktop is little different from Web Apps--you're still network intensive if not more so because now you're using a networked access to a device that itself uses network access to perform its tasks; double overhead.

Enterprise app development is really the more efficient means. The app can be made to meet the enterprise's individual needs without having to rely on more generalized applications that may be too much or too little for that particular business. Years ago--not long after the iPhone itself first came out, some businesses were already looking at how they could best use these devices. As of now, iOS devices are by far more accepted by the enterprise itself due to its relative security and--believe it or not--walled garden approach to app installation. While some of these businesses also develop Android apps for their customers, they're not readily accepting them within their network environments.