With traditional licensed software, you typically have to wait for the next release to benefit from the latest innovations or to move your organization to a new browser or operating system. Given the cost and complexity of moving to a new version, it may not even be practical to upgrade each time a new release becomes available.
With a SaaS subscription, on the other hand, you benefit from innovations on an on-going basis. As soon as a new or improved feature appears in the application, you can begin using it.