Pixel devices (at least previous ones) supported the inverse of this, where you could set the phone to remain unlocked until it was left stationary on a table. The theory is that (for some people) the most common reason to lose a phone is leaving it behind laying on a table, and it can safely stay unlocked as long as it's in your pocket.
Pixel has the feature where it can stay unlocked based on gps location (in your house for example), or wifi connection, or bluetooth connection, or if it thinks it is in your pocket. All these reduce the security overall, but it is convenient.