
If you record all your pads/midi on the fly and leave all data as is, you would never need this feature. However, if you want to refine or perfect anything or try and program something that can't be done by live human input you absolutely can't live without it. I like to perfect everything and use it every time I make a track at some point. I can think of quite a few reasons to use it:
-First you can fine tune the exact note, duration, velocity and modify attack, decay, filter or tune.
-If you want a perfect fade or curve of any of those parameters you can just step through the notes and make exact modifications.
-If you like grid X0X style programming, you can step by current TC value and program drums similarly. Not the same, but the closest you can get to this method that many still use 909s, 808s, etc for.
-Moving notes to that percise location by 96ppq increments.
-Insane note repeats higher than 1/32(3).
-Quick finding of a note (goto feature) and editing it without effecting all other data on the track. This can be helpfull when you have lots of data all in one track.
-Insert midi events. No other way to do that other than recording off midi in. This includes program change, aftertouch, midi CCs, sysex, etc. pretty much everything the midi spec has to offer.
-Test midi input. If you are having trouble with midi, this feature is awesome since you can see the data pop up in the screen. If you adjust a midi CC, you can see the bar graph move up and down on the fly.
...So not really a gimmick, just a tool available to those that need it.