The ability to get/set scoreboard values in procedures would be really useful for cases where you're dealing with handling player data that you don't want deleted. NBT data is useful but allegedly doesn't persist through death. Global variables apply to everyone so they aren't useful when players need unique values. Yes, you can use commands to set the scoreboard, but the get part is equally important.
Also, some mods have managed to add persistent NBT tags. I'm attaching a picture of the NBT values for a player who has a permanent +120 to health via the Scaling Health mod. Are the NBT tags we can add with mcreator somehow different from those?