[gumby]

IIRC Gandalf knew who old Tom was.

That being said, I thought that his appearance in the book was just a contrivance to introduce the sense that this was all middle earth, successor to an older earth older than the "old" things of Middle Earth, perhaps a purer and less subtle place.

We have such a brief time with him in the books but he's one of my favorite characters because of his hints of depth in the narrative and in himself. I think his carelessness is partially an act: sure he's old, and sure he just lives for the moment, but perhaps he knows some deeper sins he's trying to drown out with drink? Or maybe it's simply that his perspective is so long -- so much longer than, say, the elves -- that anything he encounters seems transient.

[JohnBooty]

    I thought that his appearance in the book was just 
    a contrivance to introduce the sense that this 
    was all middle earth, successor to an older earth 
    older than the "old" things of Middle Earth

Yes. On a nuts and bolts level, he has a single purpose: so that the reader knows there are things older than elves; things that elves (and maybe even wizards) don't know about.

I see why many people hate Tom, particularly many engineer-types who want their fantasy worlds to be meticulously detailed and explained.

And from a traditional storytelling standpoint, he's a total dead-end with zero effect on anything else in the story.

Yet, I love him. It added to the sense of wonder and mystery in the world. Even Elrond doesn't know about this guy? Bonkers.

[thehappypm]

He is the reason why they can kill the witch king

[p_l]

Gandalf, being older than Arda itself, has certain advantages even Galadriel does not in terms of "knowing about things" - his vows might limit him in terms of what he can do or say, but sometimes the rules can be bent.