Cloud computing is appealing for enterprises and consumers for many of the same reasons that include: Cost, Scale, Speed to Market, etc.
Existing service provider competition has consistently driven prices lower in terms of compute, storage, and bandwidth fees. Providers are also competing for having the broadest reach in terms of global infrastructure and ability to rapidly meet scaling demands of their customers. This means a significant investment in overall infrastructure to be ready to meet and serve market growth. Having excess capacity is clearly a capital investment and the desire to convert this into a meaningful revenue source is of top priority. Several of the providers are looking at the the unused capacity and a perishable asset in terms of opportunity loss over time.