Bulk sms is useful when you want to send thousands of SMS to your huge contact list. Usually the purpose here is to introduce your product / Brand / Company or a discount or offer to massive amount of people in the shortest and easiest way. Bulk SMS is more meaningful when you want to broadcast to lots of people with different level of educational quality or age. As almost all of the people nowadays have a mobile phone and use sms, it's a cost effective way to market your message to these broad category of audiences. As long as they read messages on their mobile phone you can be sure that your effort is successful.