1. On demand computing i.e. the ability to get a resource when I need it in matters of minutes.
2. Pay-per use i.e. the ability to pay only for what I use.
The rest is implementation detail. From an end user perspective it doesn't matter that much if I can get the above value from an internal or external cloud.
The nature of compute intensive loads does not lend itself to an automatic elastic resource feature, which define a cloud. We do not know if a performance bottleneck is due to insufficient numbers of licenses, or for lack of additional servers, and which servers in the cluster will solve best the bottleneck. There are tools but we need human intervention.” The commercial distributed resource management software can easily provide historical resources for billing.
A proto-cloud (my terminology) delivers now when compared to AWS EDA limited cloud implementations.
Perhaps purists are disappointed. But the customers want the fastest time to market.They can not afford to wait for that pure cloud.