I would like to provide two quick examples.
Google Chrome is not the default browser on windows, isn’t even installed yet commands > 60% market share worldwide across all platforms, likely higher on windows.
Google Maps on iPhone has reportedly 70% market share, doesn’t come even installed.
This is not to say buying defaults is a good thing, but the premise that being default automatically commands usage and people don’t switch from default would be incorrect in these glaring examples.