That was a stupid decision!

Haven't you played Mega Man 1?! jeez that was like many years and it was the shit in those days!

I have played megaman 1 alright. But that's the very first in the series so its understandable. If they had to remove the megabuster from megaman in the 9th main game in the classic series, they should have explained it as to why its not htere. Ex: it got damaged at the end of megaman 8 by the Evil Energry orb, OR it got damaged sometime after the game Megaman & Bass(which takes places in between 8 and 9.)

They didn't remove the megabuster completely, or else you would be one hit man
(Something would have happened, they ripped his arm or eventually the evil enaghy messed up his charge shot. It can be anything)