I mean, sure, once you've actually joined The Companions it is only 5 quests long. Not counting Radiant quests, of course, but the game actually doesn't let you do more that ONE radiant quest before you've completed the questline. It could do with more, clearly...
But I don't actually think that's it.
It's to do with the very ground roots of the faction's history and Lore.
So the history of The Companions begins with Ysgramor. He comes over from Atmora with 500 Companions. Jorrvaskr is the ship he travelled to Skyrim on and commanded.
Long before there even IS a Whiterun they discover The Skyforge. It's discovery prompts The Companions, as they were, to found a mead hall, seemingly using the ship Jorrvaskr to form its roof.
You think that, given the History, that at least the citizens of WHITERUN might make a bigger deal of that, if not thse in other areas of Skyrim. The Companions do not mention this either. You only learn these details from Loading Screens and the Songs of the Return books in-game.
Anyway...
This history suggest (At least to me) that there are two elements aside from the Fighting which should be a big part The Companions questline.
Smithing (I mean they've GOT the Skyforge)
and
Drinking Mead (Which is, after all, the point of a Mead Hall).
Neither of these things really play any true part in The Companions' questline.
I mean sure, The Skyforge does give you access to some unique kit. Eorland sell Skyforge Steel weapons (A tiny degree better than standard steel) and Wolf Armour (Which is actually no better than standard steel) and completing the questline also gives you access to Smithing new kinds of Weapons and Arnour (Though neither are particularly outstanding in stats).
I just find myself feeling that if the Forge is supposed be something special then there aught to be some kind of Quest involved for maintaining it. Or producing a specific weapon FROM it. I also feel like it should give some smithing quality bonus, of some kind. Something to MAKe it stabd out. I dunno...
With regards the Mead Hall part? Joining The Companions for the sixth time the other day, and listening to the swearing in speeches, there are references to both raising a tankard in your honour and leading the Campanions in song of your deeds.
And it struck me... neither of these things ever happen. Nor are possible.
For a Mead Hall, bizarrely, there is a distinct lack of revelry in Jorrvaskr.
Nobody ever 'drinks' or toasts. Nobody ever sings. There are no bards. There are no songs of deeds. Nothing.
And that, above all else, is what I think leaves this questline feeling a little bit flat. There's very little spirit of comradeship with your fellow Companions. You don't have any individual quests to do for them barring Vilkas, Farkas and Aela. The others are never defined as characters at all, and there is no option to use the Mead Hall as a Mead Hall is intended!

Is it too much to ask to offer me the chance to go out for a night on the lash with Torvar, Athis and Ria, sing rude songs, cause a little bit of minor trouble, and get a rollicking off Aela when we stagger home?! Is it!???

What do others think. Is this just me?