Apple's iMessage does just that, built into iPhone to easily gain a large number of users. WhatsApp is tied to a phone number without paying for calls. Facebook Messenge directly leverages Facebook's strong social network. Everyone has their own stable growth channels, but unfortunately Google does not. Although Android is already the world's largest mobile operating system, it is open-source and uncontrollable, and even Samsung is "digging the wall" and launching its own default SMS app.
We have experienced Google Allo before, it is powerful and has added a lot of artificial intelligence technology. However, Google Allo has failed to acquire a large number of users, and there are only about 50 million users at present. In comparison, WhatsApp, Facebook Messenger, and WeChat in China are already billion applications.
Android is definitely Google's most powerful card, but maybe that's why Google is using it more cautiously. It's not impossible to push the pre-installation like iMessage, but it may lead to protests from carriers who won't like having such a service on Android phones that can replace SMS. It is estimated that 8 trillion text messages are currently sent based on SMS services every year, which is a huge and unforgiving market.
After considering various factors, Google's choice to use Chat to upgrade its existing SMS text messages became a reasonable and inevitable choice. Android is an open system, and the SMS system needs to be upgraded, which is also in the interests of operators. So what will be different about the new Chat?