Google has been particularly slow with rolling out Assistant Driving Mode, which was announced at I/O 2019 but only made available in late 2020. Even then, it was limited to users in the US. But that's no longer the case as Google is now making the feature available for users in other countries too.
Google has spent plenty of time this year updating its products to be more useful during the pandemic, and some of it's freshly announced Maps features serve that same purpose. Improvements to the COVID layer and live information about how busy buses and trains are will help to keep us safe when out and about, and the much-anticipated Driving Mode is finally arriving in preview.
You've always been able to run the Android Auto app on your phone to get a better/safer interface while driving, but Google doesn't widely advertise that functionality (the Auto app is mainly used for connecting to car entertainment systems), and it doesn't always work correctly. Google announced a replacement over a year ago at Google I/O, and it's finally showing up on phones.
Quite a while ago, along announcing the new Android Auto experience, Google also said that it would deprecate the interface for phones completely. It encourages its customers to use Assistant Driving Mode instead, which is poised to come out "this summer." Android Q is apparently already preparing for this, as some users on the latest beta report that the Android Auto app icon is disappearing for them, with no option to start the app from their phones anymore.