It's just a differentiator. It's actually tied to the Phone by Google app, but some features only work on Pixels (and maybe other phones that have it pre-installed as the default dialer, but I don't know which those are). https://play.google.com/store/apps/details?id=com.google.and...

It does work well though. I get a lot of spam calls and texts a month (the result of my political donations, which I didn't realize were public info and easily harvested by spammers, sigh... fucking NGP Van). The Pixel filters out the overwhelming majority of them, thankfully. The call screening works exceptionally well for spam calls, since most just hang up.

The Pixel is a perfectly generic phone, IMO, but the spam blocking is amazing. I switched to an iPhone for a few months, but the spam (even with several third party apps) made it unusable and I eventually got another Pixel instead. About the only thing it consistently does better.

Pixel phones are not Nexus phones, they aren't just running stock Android — they have custom features to convince users to buy them.