Because Rivian doesn't have a mode for _just_ lane-keeping. There's Adaptive Cruise Control (which maintains speed) and there's Highway Assist (which maintains speed and position in the lane). Highway Assist only works on certain mapped highways.
At least for me, most incoming calls are spam. If it's important, I will either anticipate it or the caller will leave a voicemail. In the past several months, I think I've received one unanticipated call from a friend.
Early thirties here: my friends and I do not call people except for older relatives on occasion. We've kept our phones on vibrate for a decade and a half now.
We do, however, know our own phone numbers, and asking a cute stranger or a new friend for their number is still a thing.
I haven't found exact data for the contribution of ICE vehicles to PM 2.5 levels in Denver, but I've found some evidence of ozone [0] and carbon dioxide [1] contributions in Denver being around 30%, as well as contribution to PM 2.5 in "developed countries" being 25–30% [2].
Later edit: this EPA paper from 25 years ago [3] says "Vehicle exhaust was the largest PM 2.5 carbon contributor, constituting ~85% of PM 2.5 carbon at sites in the Denver metropolitan area".