The point of not having a steering wheel was to experiment with a platform where it is assume disengagements where user intervention is needed in an emergency won't happen, because Google's own research indicates that relying on disengagements is dangerous.
Level 2-3 cars are frankly, too dangerous for the road IMHO, and the rush by automakers to ship these out to the public is, I predict, going to lead to some serious disasters, class action lawsuits, and regulation, that imperils the whole enterprise.
If there's anything that you don't ship "until it's ready", it's a device that's lethal to human life when something goes wrong. Tesla already killed someone, and while you could argue he violated the beta test agreement, shipping cars which requirement drivers to be attentive and keep their hands on the wheel while self driving -- ready to be aware and take control at a moment's notice -- effectively are engaging in bullshit marketing, because we all know that people who use self driving don't want to sit there "engaged" but want to be free to do somethings like check their phone.
Public data on disengagements shows Waymo is far far ahead. Are disengagements important? Yes. Every disengagement is a failure of the car's automation to handle road conditions that would require emergency intervention by the driver. But keep in mind, Waymo drives off the highway as well, whereas many of the competitors with worse disengagement figures are triggering them on mostly highway driving.
Taking time to do this right might be frustrating to those who want products shipped immediately, but the first time a level 2-3 car runs over a schoolyard, people's minds will change very fast.