Well, this is made as purpose, you have to get timing in the start and in the end of the longnote to don't have a miss or a score reduction, and obviously a ComboBreak... if you play Beatmania IIDX or O2Jam you'll see that's the same, this mode emulates them, it isn't a turned down dance game...
It's a BeatGame. DanceGames are music games designed for everyone to play them...
BeatGame's are the ones that hardcore music gamers have tendence to play... they have harder hit-windows and that makes the accuracy harder to get 100%, and even if you get 100%, the score surely won't be the MAX Score.
Until you got an FULL "Colorful 300" (aka JustGreat [Beatmania Term])
Basically, in BeatGames Perfect Accuracy means the Best Score, it's really the oposite as Osu! Standard, there Combo got almost the same Weight of Accuracy or even more than accuracy in the score calculation...
Actually, i don't want to get a discussion that will be endless, but i think a GOOD PLAYER don't need the combo bonus to show his skills, and that's really the only weak point of Osu!, and really, Peppy knows it... and he admit that fault...
And he thinks the same way, but restarting all the ranks will make the 'Best Players' and the 'Popularity' of the game go down in a straight line, so he doesn't give it a chance for modify that...
Personally i think that Osu! in the 5th anniversary needs a start from scratch, and a new Score Calculation would be the perfect thing to introduce, even knowing the "Mass" will be against this change...
But, this is a Peppy's decision. I can't say more than this, but, get used to it...