There are three basic categories of notification system:
Public: These are the government sponsored programs where federal, state, and sometimes local government works with telephone and wireless companies to provide types of warnings, such as Amber Alerts, to devices. Normally the operating system allows opt-in or -out of these notifications.
Corporate-sponsored: Most people are familiar with, say, television stations scrolling school and sometimes company closures along the bottom of the screen. While to some degree there is “serving of the public interest”, these are basically marketing programs designed to enhance viewership. Similarly, many media outlets allow you to text a keyword to a short code to receive some sort of alert, often related to weather but other messages could be piggybacked along with those. The business concept behind those offerings is to build awareness of and loyalty to the provider of the messages, and sometimes to sell other goods and services.
Private: These are the mass notification systems that YOU control. Obviously they are essential because while a corporate-sponsored system might alert you to the fact that there is a snowstorm in the area, you need a private system to provide whatever details apply specifically to your organization. And the fact is that the vast majority of notifications that are sent via a private system like AMG Alerts do not deal specifically with anything weather-related (at least in a macro sense) but instead issues that are unforeseen: security issues, system failures, and other localized phenomena.
Certainly there is a place for all three layers because they serve different purposes.