You would be surprised how often people just use a (repeatedly) sorted vector in spite of a proper data structure or proper insertion calls. It's a lot simpler to just append and sort again. Or the appending happens somewhere else in the code entirely.
As a real-world example, consider a sprite list in a game engine. Yes, you could keep it properly sorted as you add/remove sprites, but it's a lot simpler to just append/delete sprites throughout the code, and just sort it a single time each frame, even if it only adds a single sprite.
So yes, technically this pattern is not needed if everyone always recognized and used the optimal data structure and algorithm at the right time. But that doesn't happen, and it isn't always the simplest solution for the programmer.
As a real-world example, consider a sprite list in a game engine. Yes, you could keep it properly sorted as you add/remove sprites, but it's a lot simpler to just append/delete sprites throughout the code, and just sort it a single time each frame, even if it only adds a single sprite.
So yes, technically this pattern is not needed if everyone always recognized and used the optimal data structure and algorithm at the right time. But that doesn't happen, and it isn't always the simplest solution for the programmer.