You're perplexed because you are looking at the issue backwards.
The Ranger was a Fighter subclass to mimic Aragorn. Fighter was chosen as Aragorn, like the LOTR Rangers of the North, was a warrior .Aragorn could not be a fighter as the D&D fighter had no explicit skills. Even when newer edition gave fighters skills, it didn't get ourdoormanship, mundane nor fantasy.
The thief and later rogue had skills. However the thief was a terrible warrior and the rogue only slightly better.
Fighter: 90% Fighting, 10% Skills
Rogue: 10% Fighting, 90% Skills
Ranger: 75% Fighting, 75% Skills
To balance the ranger, the ranger's scope of fighting styles and suite of skills were limited. And since some skills were not fully implements, those skills became spells.
And that's why the dual wielding, beast speaking, green hooded ranger became a class, stayed a class, and wont merge with fighter nor rogue.