The Nexus 6 would have featured a fingerprint sensor if not for Apple

The Nexus 6 was originally scheduled to feature a fingerprint sensor where the dimple is located at the back, but the idea was ultimately foiled by Apple. Motorola was working on fingerprint recognition with a company called AuthenTec, with devices from as far back as 2011 featuring the technology. However, Apple acquired AuthenTec in 2012 for $356 million to use the technology in the Touch ID sensor, which meant that Motorola had to look elsewhere. According to former Motorola CEO Dennis Woodside, other options didn't quite cut it, meaning that the feature was left out from the Nexus 6.

source: androidcentral