"better app" can just be an app with less features, that's more buggy, that's going to be around in ten years. Mom and dad don't need to go learning a new app every couple of years.
Video chat has been around since forever. Having a major player like Google wade into the fray, destroy all the small fry, then bail out (as it has done many times before)? Not good for the market.
Skype was launched in 2003, and IIRC was primarily voice for the first couple of years. That brings us up to the 10 years that's apparently the required expected longevity to even consider an app.
Whatever small fry exists on the market, they have survived the Skype juggernaut, FaceTime, Google Hangouts and Facebook chat. I find it highly unlikely that Google Duo is going to be a uniquely destructive force.
Video chat has been around since forever. Having a major player like Google wade into the fray, destroy all the small fry, then bail out (as it has done many times before)? Not good for the market.