Well I honestly searched and I couldn't find anything... so here goes nothing.
I'm sure a lot of you will say common sense but...
Say maybe you want to play horde if you're alliance or vice versa or you want to play with someone you know on another server. Or maybe you just want to reroll on another server altogether, but you don't want a death knight to be your main on that server.
We all know how boring and annoying it is to get gold on a low level character.
Just make your new character and then create your Death knight, very simple.
Now you either have 2 choices:
Do all of the Death Knight quests, Send gold, delete, repeat.
Do enough death knight quests to get to Noth's Special Brew.
2g 50s each 5. Continue doing this quest to get the potions as they vendor for 2g 50s each 5.
I'm sure parts of this have been posted but I'm not sure about the entire thing.
You can also use this to have enough money to buy some blues for your leveling or to farm for your level 30 mount quicker. I know it still takes time but it's easier than making 30s after like 50 quests starting from level 1.