Security systems work by making it harder for things to get done. Security creates more friction in the system. If you have enough momentum you can overcome the friction, if you don't then you get stuck. If a cyber criminal has the login and password for a user, the security systems fail because he has taken the low friction path that gives him access.
Legacy IT systems are rampant with systems and processes that create more friction - standards, meetings, specifications, requirements all usually make it harder to get things done.
The Cloud is easy. Login, give them a credit card number, request a service, and it is up and running in seconds. The Cloud focuses on less friction and that is why it is winning.
Who would want a cloud service that took just as long as a legacy service, eating up your time and money just like you have always done in the past. Whether it is virtualized or not who cares? Well VMware does care, but most of you shouldn't really care if it virtualized environment.