With Diceright (and Im sure with other VTTs), my goal was to help streamline certain aspects of the game so players can focus on the fun stuff. Mostly around combat and tracking all your character details. So for combat, on Diceright, you can target enemies when you attack and then when you damage them, the player gets an alert with a CTA to apply the damage - so players aren't always asking, wait who did you attack? How much was the damage again?
And on the character sheet side, with a standard character sheet, I've often found myself looking at my AC or one of my stats and not totally remembering how I got to that number. Diceright keeps track of all your bonuses for you and shows you how your stats were calculated.
Those are definitely all things you can do on your own, but it can be nice to have a computer automate them for you.
Again, totally agree that the system you've got works. Just sharing some of my considerations when I went into building this.