Normally, I'd agree with you -- defaults are a very, _very_ powerful thing.

But if you're using Google's web tools, they make it (too) easy to download their apps and push you in that direction in a million little ways. For example, GMail's native iOS app will either open a link in a WKWebView or Chrome (if it's not installed, it'll prompt you to install it), but you have to jump through some hoops if you want to open a link in the system's default browser. Similarly, if you're searching for something via google.com, they'll put up a prompt to download their search app, with the default "Continue" option taking you to the store rather than continuing with your current task (and then click-jack the back button).

the default windows browser has somewhere between a 5% and 13% market share. i think you're the one overestimating the power of defaults here.