Rebranding requires big promotion and a lot of money. Sometimes it is more simple to create a new project and start to promote it then to rebrand the old and forgotten one.
exactly what most of developers has been doing, abandoning old project and create new one because it's simpler.
for example is the case of FTM to Sonic, on the process of rebranding they diluted the coin and there's long running campaign where they allocated big chunk of coin to attract new users and to let the world know that they have rebranded themselves, but we're still seeing whether it will works or not, so far, they've been gaining new users though.