The subscription model allows the vendor to make strategic, long term-ish decisions around hiring and enhancements, knowing with a high degree of certainty that

The subscription model allows the vendor to make strategic, long term-ish decisions around hiring and enhancements, knowing with a high degree of certainty that the money will roll in each month to fund these plans of world domination. It wouldbe very hard to run a SaaS business with totally variable monthly revenues.