Why and how do they lose the rights to certain Transformers names?

For example...



Jazz now has to be referred to as 'Autobot Jazz'



Ravage now has to be referred to as 'Battle Ravage'



Hot Rod now has to be referred to as 'Rodimus'



Does Hasbro not keep up the copyrights on some of their most classic characters?Why and how do they lose the rights to certain Transformers names?It could also be that the basic names themselves would not be copyrightable. For example, Jazz in and of itself may not be original enough to copyright, but Autobot Jazz is definitly something in particular. Ravage is a standard english word, nothing unique, but Battle Ravage is different. There are even magazines named Hot Rod but I've never heard of a Rodimus.Why and how do they lose the rights to certain Transformers names?It is likely the opposite, those particular names were already copyrighted and Hasbro had to change them to avoid problems.