ever wonder why do some riders choose to have custom looks for various races - see valentino, lorenzo,JT,casey & nicky (@ their home races)?
while others never change anything: Repsol boys
It’s because Hondas are boring. 
Ducks!
yea, cause the Rizla boys change all the time.
The reason probably has something to do with riders’ contracts - which allow them or require them to do so, but must be due to the riders’ creativity as well.
Sponsorship $$$$$$$$$$$$$$$$$$$
some riders are more interested in the racing than looking good
Rossi is a master at marketing though, he changes his helmet design every so often and does so with consumate marketing expertise.