A perpetual license is one that you pay for once and you can use as long as you wish. Often software services are delivered as an annual subscription. This is common for cloud based services. So why would anyone choose a software service if you have to pay annually? Lets look at the advantages. A software service is much like a rental. In this case you should not have to pay such a large amount up front, reducing CapEx. The software can be upgraded at no cost so no more old out of date solutions. The user can often avail of additional services such as remote support, and features that can be metered such as cloud storage.