Ok, I’ll go first: feature testing is motivated by a desire not to be busted, particularly in the face of new versions of UA’s which will (hopefully) improve standards support and reduce the need for hacks in the first place. Sensible enough. Why should users wait for a new version of your library just ’cause a new browser was released or because you didn’t test on some version of something. Cutting The Interrogation Short | Infrequently Noted
It does make sense that if you already know what a browser is capable of you stop trying to detect every single feature and only do that when you don’t know what browser is being used.