Probably the top reason I wanted to get GrapheneOS was the privacy/security aspect of it, this includes: no google play services by default, multiple user profiles (more than the Stock OS can have), a network permission for apps (this normally can't be toggled), disabling all usb data connections (can easily be activated in the Settings if I need it), Bootloader can be locked again after flashing the ROM and much more.
It also has very frequent updates, and my phone will get them for a long time (also true for the Stock Android on Pixels, but that one really sucks), which was also very important for me, as I want to be able to use my phone as long as possible.
What made this even more appeling is the possibility to install sandboxed google play in a seperate profile/user for apps that really need it, which works surprisingly well, and even then the google play services don't run with elevated permissions like they normally do, but with the same permissions like other apps.
And the battery life is insane, if I don't use my phone it basically does not loose any battery, and even with heavy usage I don't need to charge it daily.
So GrapheneOS was the easiest way to start degoogling (kind of ironic using Google Hardware) my mobile phone, while still being able to run nearly all of the Apps I need.
Oh right! I think I have that on a tablet. I was confusing it with the alternative to Android that Google is developing when I asked you about it. Thanks for the info.