This question has already been asked and addressed in previous threads,!
and this is not a discussion post.
but for the record,once and for all...
There is the factor that graffiti in this context began in romanized places,
also the factor of increased readibility and hence recognition ,especially in "the scene",
and the fact that Japanese characters are ridgid, with many detachments and pieces making them difficult to work with.
This thread is'nt a complete or pure representation of all graffiti in japan,
it's picture collections of (mostly western) people.
Things look different when you're there...
and P.S.
look again.
Flicks.....