Material design is a set of design guidelines and principles developed by Google. Adopting material as a design guidelines guideline is beneficial for many reasons,
Clean, consistent look and feel across web and mobile
A clear set of rules for use of fonts, color, shadow, buttons, text, headings, etc.
Using an established common design language and rules makes it easier for developers to contribute to our UI/UX
Similar look and feel and components as in many other apps that users will be familiar with (WhatsApp, Gmail, Contacts). This makes it easier to train low literacy users since they would already be familiar with UI elements such as Floating Action Buttons or Navigation drawers.
A library of plugins and frameworks are available for easy implementation
Frequent updates and strong support from Google
...