What I don't understand is why the Lion Voltron is more popular. I heard it was because it had a better story and better characters. Plus, Lion Voltron came out first so I guess people just latched onto that as the defining Voltron.
I think there's something more iconic about the lions plus they were cool looking on their own before forming Voltron. I say this though as someone who never actually saw Vehicle Voltron, it was like an urban legend when I first heard of it in those pre-internet days. I'm not sure it penetrated as many markets as the first Voltron. Maybe not unlike Robotech where the Macross part has much more presence than the later series merged in.