Google came up with the option of changing your default texting app in 2014, they also enforced this rule on other phone makers as well, convenience and security were chief among the reasons for this decision but the option of having a texting app that was different from the one on your phone was the important point.
It is a common misconception that all Android devices are made the same and that it is just a matter of choosing the cheapest possible one, for instance, the version of Android that can be found on Samsung devices is a variant of the traditional Android device with patches applied over it.
The default texting app on a Galaxy S7 or Galaxy S8 can be changed in a completely different part of the settings. The version of Android that can be found on Samsung devices have patches applied to them.
i) Confirm your choice by selecting OK.
Most SMS apps will hit you with a prompt asking you whether you wish to make the app your default messaging app on opening it for the first time. But there are exceptions to the case, for example, Facebook Messenger, certain apps do not provide you with a prompt once you have initially dismissed it.