Why do they need to transform bumbleebee from black to yellow?
Why do they need to transform optimus prime from the rusty mode to the western star truck?
Why do they need to make drift a triple changer?

Its about milking the character with different colour n physical...
And also dont you feel that a character cant last for 2-3 movie and they will kill it off?
Because they dont feel like to reuse the same mold for the same character because mostly ppl wont be buying
the same toy again and again...
Even if it survive they will change its apperance...

Boring because of the same physical and appearance is not a good answer because I dont mind watching G1 optimus prime over and over again...

And yeah, they wont kill bumbleebee yet because kids just love it...
And also they wont kill optimus prime because they just cant...