Despite other Autobots having the ability to speak, Bumblebee is unique in that he cannot talk in Transformers - and there's actually a perfect reason why in the franchise's own canon. Starting in 2007 with Transformers, the live-action franchise revived the idea of large sentient robots who disguise themselves on Earth as vehicles from the original cartoon series of the 1980s. The films follow the continuation of the war between the Autobots and the villainous Decepticons after the destruction of their home planet Cybertron.
Though the franchise changed a lot since Michael Bay's 2007 movie Transformers was released, many of the ideas introduced in the initial film have remained consistent throughout the franchise. The first Autobot introduced in Transformers was Bumblebee, who was set apart from his fellow Transformers by his inability to speak. Instead, Bumblebee uses clips of audio from songs and movies to communicate, allowing him an extra design quirk that further distinguishes his character.
However, despite Bumblebee being one of the most recognizable characters in the live-action Transformers franchise, he is the least vocal of all the Autobots. His inability to speak within the franchise is revealed in the character's self-titled prequel movie Bumblebee. Upon being sent to Earth by Optimus Prime, Bumblebee is hunted by Decepticon Blitzwing, and he refuses to give up the location of his comrades. As a result, Blitzwing destroys Bumblebee's voice synthesizer, damaging it beyond repair, which prompts him to learn to use clips of audio to communicate.
By having Bumblebee explain the original Transformers movie's biggest unanswered question, the prequel gives its titular character an appropriately righteous backstory. Bumblebee nobly sacrificing his own voice to save his friends is an excellent way of establishing his heroic nature while simultaneously giving an irrefutable answer to the franchise's most persistent question. This makes the decision to finally reveal the depth of Bumblebee's character in his solo film feel justified, but it was an absolute necessity in order to make the character's story make sense.
Interestingly, Bumblebee was originally mute in 2007's Transformers for reasons outside of the film's narrative. The decision was made in order to give the characters of Bumblebee and Sam Witwicky a deeper connection that went beyond words. Though many things are considered to have gone wrong with Michael Bay's Transformers movies, this decision wasn't one of them, as Sam and Bumblebee did indeed share a close bond that was one of the best aspects of the early films' stories.
Ultimately, Bumblebee's inability to speak in Transformers was the result of a noble sacrifice made upon his arrival on Earth. However, the behind-the-scenes reason for the choice was equally fitting, allowing for a better connection between the franchise's human and Autobot characters. Though Bumblebee wasn't able to talk in Transformers, he was still able to prove one of its strongest characters, which is all the more impressive for it.
