For Android users who love tinkering with their devices and customizing it on a deeper level, chances are you have unlocked your phone’s bootloader. This is pretty much the only way to go about it if you want deeper customization and to install apps/tweaks that might require this level of access.
However unless you know what you’re doing, unlocking your device’s bootloader can be a security issue, which is why it has been recently discovered that Google has made some changes in the Android 7.1 beta that will make Android Pay no longer work with devices whose bootloader has been unlocked, or if the device has been rooted.
The reason for this has been speculated to be that Google is trying to make Android Pay as secure as possible, and devices with their bootloader unlocked and with users having superuser access to Android, they could figure out how the system works and create hacks that could potentially steal credit card information from users.
That being said, Android Police seems to suggest that this could potentially be a bug. This is based on a post on Reddit in which users who complained about this issue to Google were told to submit a bug report, meaning that perhaps it might not have been intentional. However given that Android 7.1 is currently in beta, we guess we’ll have to wait and see if the issue remains even after it is released, in which we can only assume that it was done on purpose for security reasons.