when spacies are trying to sweetspot the ledge while recovering from above the stage, dash attack can cover most of the angles, and then subsequently set you up for a free followup most of the time (dsmash, dair, nair) .
Dash attack is also good when your opponent is in shield. depending on the character, if you know that they are going attempt to aerial OOS or wavedash OOS, you can clip them with dash attack while they are still in the jumping animation before anything comes out. This is all or nothing though because if you straight up hit their shield with a dash attack you'll eat a hard punish.
when comboing characters that float a lot, there are certain percents where dash attack can combo very well into other moves after a hit confirm.
when comboing fast fallers, you can use dash attack to interrupt the timing of their techs. since this game punishes people for mistiming their techs, you can dash attack at certain points in the combo to throw their timing off and put them on the ground to potentially get a followup.
https://www.youtube.com/watch?v=_jeNFmmf6Kk