Despite smartphone ownership in the US doubling in the past five years, there are many people who still do not have access to Mobile Internet Devices (about 102 million at last count). However, 98% of the population does have access to a cell phone or other device capable of receiving SMS text messages.
This is why a lot of nonprofits, businesses, and even emergency response teams take advantage of text blast software to quickly broadcast messages in a format that almost everyone can receive very quickly.