You can thank Wally Burr, the voice director, for that. Before the Sunbow stuff of the '80s, most cartoons were thought of as a quick two hour job that a voice actor could do in the morning and be on to his next gig after a fast read. Burr, now empowered by the substantial (for the era) budget provided by the fact that these cartoons were funded by the toy companies as marketing tools, decided to give the clients a product they could be proud of, and brought the hammer down on the actors. He forced constant retakes, hours of rehearsal and recording and group performance, research on characters and making each character unique, and enforced the adage that a cartoon was really a radio play with pictures. Between Transformers, GI Joe, and other Sunbow cartoons, Wally Burr essentially created the modern idea of voice acting in cartoons (and eventually videogames), inasmuch as taking the job seriously and trying to perform the material straight, even when it was absurd.
As a result, these characters became vividly depicted aurally, and they stuck in our heads. A tremendous amount of the nostalgia and memorable elements of Transformers and its ilk come from the performances, and those performances are the result of Wally Burr settling for nothing less than excellence from his actors. Dude is in his 90s today and still teaching voice classes and directing projects. Extraordinary man.