I've bought a few first aid kits in my life and the best of them is in my boat......as I've learned that that's where it most often needed. Fishing is actually more hazardous than hunting....
But lets define what a first aid kit actually is!!! Go to any retail store to buy one and what do you actually get? Well it seems to depend largely on where you go and I've found that if you're lucky enough to know a RN she (usually) can make up one better than you can buy!!! (ASSUMING YOU KNOW HOW TO USE IT) and there's no way it can be carried with you always.
However there is one component of a good first aid kit that is always with you if you get it and that's education.
Being able to perform CPR is vital and not something you buy in a store.....One can tear off his T-shirt to be used as a gause in an emergency and all you need thereafter is knowlege. It's not clean you say??? What else do you have?!!! The shoestrings in your boots can be used to attach makeshift splints if it's necessary and all one really needs is a nifty jack knife which seems to be in my pocket all the time.....
My point is that the one most basic component of the first aid kit is a good first responder course and a follow-up every couple years....its education and if you take that hunting you're far better off than one with an official first aid kit with the name "Cabelas" on it. Just add a pocket knife which most of us have anyway.