The answer is quite simple, better service and superior product.
In the old days before the cloud you used to buy software outright, manage it yourself and pay separately for support and maintenance. Part of the management of the software was making sure your systems were in good shape and taking regular back-ups. In most a cases people were too busy to do these things and then it would happen a dead hard-drive leaving you with no data. Recovery was expensive and could dramatically impact your business/life.
In the cloud era all of the headache factors (back-up, security, etc) are taken on by companies like ABAKiS as part of the service and all you need to do is login from a browser. Support is included with the subscription so no worries if you need help.