Originally posted by Thomas Riker:

They're one of the very few things I regularly forage IRL. They're always present in this genre as decorations, but you can almost never eat them. Just seems odd.

In The Long Dark cattails are a very important resources.

Most games are not meant to simulate real life though. They are just mechanics meant to make for an engaging game.

Sure, cattails could be made edible, but we already have raspberries and mushrooms to do pretty much the same thing - it wouldn't introduce a new mechanic. Plus, you can create infinite cattails with the cultivator.