One of the things people most liked to get angry about regarding Google's Pixel and Pixel XL smartphones recently was the update situation on Verizon. As you may know, if you're in the US Verizon is currently the only big carrier selling them. You can also grab a Pixel from the Google store or Project Fi, but not AT&T, Sprint, or T-Mobile. At least not yet. Add to that the fact that Verizon really isn't generally known for pushing software updates quickly to its devices, plus a poorly worded statement by a Google spokesperson saying "Monthly security updates will come from Google, and...
Source: http://www.gsmarena.com/pixels_sold_by_verizon_will_be_unlocked_receive_updates_when_google_pushes_them-news-21030.php