It's also good for low level crafters who are leveling and don't get good XP anymore from crafting some low level items.

Like, for example, making cotton cloth doesn't return good xp after a while but you need to make tons of it for the other recipes that DO give good xp. SO! What you do is buy from the vendors to help on efficiency.

It's also nice for when low level stuff is gathering or mining only and those peeps have been lazy.