Their robot modes would still have components to their Earth forms, but this was mostly done to cut down on costs and making new cartoon models.
In some new media when depicted on Cybertron yes they do appear to have Earth forms, but even then going back to G1 some robots had Earth-like vehicle forms even millions of years back, such as motorcycles, trucks and construction vehicles, but with a futuristic tone.
They freaking just murdered Wheeljack like he was nothing. People cried over Prime. And they was like what the fuck is a Wheeljack.
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Bender: Well, everybody, I just saved a turtle. What have you done with your lives?
