The dwarves want to return to it for the precious metal Mithril . This was the original source of the dwarves' wealth. Ironically, it was also the source of their downfall. They mined too deep and released something evil and hideous. When they were producing mithril everyone wanted it.
Elves love it.
Sauron covets it. Bilbo's mithril coverlet was worth more than all of the wealth in the Shire put together. No one knows that Frodo is wearing such an expensive item. Most of the company falls to sleep. Gandalf expects it to be difficult for them to find their way to the door.