I wouldn't know about the Japanese, but Infidelity has posted recently on ACMLM or whatever.
It's just really hard to hack Mega Man music and make it sound "Mega Man" like, especially when compared to doing it in programs which have little to no use for NES projects. Also the same reason why so many MM hacks reuse the old bosses while many MM fangames have original bosses of exceptional quality.
They just don't care about the NES. They're the complete opposite of the Sonic fanbase. Those guys would go to extreme lengths, which is admirable, but the MM guys just fire up Flash and call it a day.