Quote Originally Posted by GoktimusPrime View Post
Perhaps one reason why they didn't give Siege Prime his G1 Cybertronian mode was because they already made Siege Megatron a tank, and they didn't want two tanks in the same assortment. Of course, the alternative would've been to make Siege Megatron into a scifi gun or space cannon. Still too similar? If they really wanted to go with a Cybertronian truck, then they could've given that toy Optimus Prime's (canonically) earlier Cybertronian mode.

While G1 Prime's Cybertronian tank mode was seen first (in #1, 1984), his Cybertronian truck mode was seen in a historical recording back when Prime was a junior ranking officer (as seen in #48, 1988 - hence the Triggerbots). But either way, it's also a G1-accurate Cybertronian mode for Optimus Prime and it would have also satisfied retail buyers in not having two tanks in the same assortment.
Now that you mention it, what would have made a lot of sense is for Hasbro to have made Prime a "tank" as seen in the comics and make Megatron something else - either a jet or space gun. That way, they are much more different to their Earthrise counterparts and more people might feel inclined to have both versions of them instead of picking and choosing. We know that Earthrise Prime shares parts with Siege and by the looks of it Earthrise Megatron is a retool of Siege. Regardless, they are very similar toys.