They do in this case. The reason people are saying Carol isn't likely to be leading the Avengers in Infinity War is that barring some retcon about her having been active before all this, she'll be a relative newcomer to the world of superheroics, which is why the comparison to Captain America doesn't hold up. He wasn't just a seasoned soldier when he was made leader of the team. He was a seasoned superhero. They aren't gonna make someone who just became a superhero 10 minutes ago into the leader of the Avengers.
We know you like Carol very much. She's just probably not gonna be the leader of the Avengers in Infinity War. I said the same thing when someone in the IW forum said Spider-Man will be leading the team in the movie.
I still don't follow. Superheroics are really no different than heroics. In TFA, I saw Cap more as a soldier than a superhero. He lead The Howling Commandoes, which was a small squad of soldiers with no powers. How exactly did that prepare Steve for leading a team of exceptional people with exceptional abilities the likes Cap has never seen before?
I'm sure Cap will be the leader, but it sounds as if the Russos want to put a larger focus on some of the newer Avengers since Cap and Iron Man have plenty of character development as it is. If phase 4 is the start of a brand new Avengers team of Avengers in the lead, then maybe that is set up as the newer heroes take command at a crucial moment in part 2. Maybe it's more T'Challa, Carol, and Strange than Iron Man, Thor, and Cap.
Now, I'm pretty sure Carol won't be leading the Avengers, but I could certainly see her take the lead at some point within a 2 hour film and it could be that she is the best equipped to lead AT THAT TIME. Given her origin involving aliens, maybe she knows something the Avengers don't and time is crucial. She isn't necessarily going to get Captain America's approval. She's going to take the initiative because she's the only one that knows what needs to be done at that time.
Often times leaders aren't necessarily chosen, but they take command and people get in line because that person knows what they're doing.
Okay, I'm biased. I'll admit that, but that doesn't necessarily mean I'm wrong.