Buy Samsung phones instead of Pixel phones, and use the feature every single day, and convince a few million other people to do the same...

Otherwise, if the usage for a feature is low, they won't do it.

I work at Google on not Android, but Chrome OS, which does have video out, because we are a desktop/laptop OS not a phone OS... It took us years to get the extended display/mirrored display experience to be smooth, so it's not something that can be done easily!

Even Apple on iPadOS it's a clunky experience to drive an external display.

Practically speaking if your OS isn't designed with mouse + keyboard in mind, you're going to have a bad time, with an external display.

If your answer is, well I just want to use it as a tethered casting interface, no need for window management, that's another story, but it's also really limiting and of limited appeal since Google is pushing wireless casting with Chromecast and other devices anyway!

So you can see there's a challenge in engineering, and in user demand.