If you're in a situation where your phone has data, but your tablet doesn't, and Wi-Fi isn't an immediate option, things can get frustrating pretty quickly. Consider checking into a hotel, for example, which only allows one or two devices to connect to the Wi-Fi - that's a major roadblock for those with their families, or those with multiple devices. While your smartphone is charging, you could be kicking back using the tablet, for example. That assumes that the hotel's Internet service allows you access without dinging you again for another device.
Situations like those or similar will be less of a problem going forward for Android users with Google Pixel or Nexus devices. In the Google Play Services 10.2 update, it has been discovered that if an Android phone connected to a Google account has data access, then another Android device will be able to tap on its connection automatically.
Before anyone freaks out, yes, the automatic connection would only happen after initial setup of the devices. What the feature is meant to do is increase the convenience of keeping all of your devices connected, as long as your phone has a connection. It's not clear at this point if Wi-Fi enabled on one device would also be automatically shared, not only the cellular data connection, but we can hope so.
Given the convenience this kind of feature could offer, we'd also hope that it won't remain exclusive to Pixel and Nexus devices for long. After all, there are a few million other types Android devices in use today.