Medabots have personalities without rare medals, though. Like Prostagma said, rare medals are just used in the anime to have a batshit plot about robot civilizations, justifying power jumps without the need to change the protagonist medabots' parts around and limiting the use of Medaforce to a plot superattack for coolness reasons. Not to mention "oh my dad works for the corporation so I got the one of a kind, incredibly unique artifact usually locked in max security vaults" would probably get the dad fired and the medal repo'd.