1) See what is currently craftable in your character's professions and the mats required;
2) What mats your character has on hand (trivially easy, since that's already reported in the Create Auction part of the RAH)--optimally you could from there easily buy what you need in the RAH and have it added to your stock;
3) Allow you to craft the stuff remotely so you can sell it in the RAH. It's not like it's a huge advantage, but it's something to allow us to make better use of the RAH when not in-game and more efficiently use our actual in-game time. An added bonus would be the ability to mail crafted stuff to other toons on the same account, but that's not a necessity.
WTB Suggestion Forum, but this was as close as I could come, since it really just relates to crafting professions.