Google's Messages app is packed with features, including a built-in markup tool, reminders, context-aware recommendations, a dark mode, RCS support, and a web interface. Most of these aren't available in other texting apps, especially the ones manufacturers pre-install on their phones, which make Messages particularly popular. In fact, it's so praised by users that it just passed one billion downloads on the Play Store, less than a year after reaching half as many installs.
The app isn't part of the GMS (Google Mobile Services) package, meaning most manufacturers ship their phones with their own texting app instead of this one. Only Pixel and Android One handsets come pre-loaded with Google's Messages app. This important number of download means an impressive number of people chose to replace their default messaging software with this one.
If you're not part of the one billion people who've switched to Messages, I recommend you download it using the link below, and you probably won't go back to your manufacturer's solution.