Effect entry/exit-time in cues

I know that this was handled like this for ages and it's probably a question of philosophy but here goes:

Why do effects always use the Up-time, when referencing Cue/Sub as the entry or exit time.
It never really made sense to me but only recently bothered me, so I'm bringing it up now.

Wouldn't it make more sense for an Intensity-effect to use the Down-time for exit time?
The same goes for Focus/Color/etc.-effects and their respective times.

In most situations this would be the desired behaviour, at least in my mind.
And if it's not in some cases, you can still set discrete times for the effect.

Am I not seeing something here (might very well be the case)?

Kindest regards

Also a related feature request: Could we get a "MarkFX" softkey?
It could move the fixtures to a starting-position, similar to starting a focus-effect with a rate of zero, but respecting mark timing.