It’s only important because its punishing.
And the weight of quivers does make it trivial when encumbrance is 15*STR lbs and a quiver weighs 1lb 20 arrows weigh 1lb.
10 lbs of weight is 100 arrows which would last nearly 198 rounds on combat on average (which is 50 combats or 8 “adventuring days”) and worth a good 4 levels of xp.
Even with the more restrictive encumbrance rules, 2-6 lbs of weight means you will not have to buy arrows again for maybe in a year in real time.
Its a a bunch of effort to solve a problem that doesn’t need to exist.
When it comes to snidge if you look at the tone of the game they are playing and consider that they havent diligently tracked arrows saying “you should have been tracking arrows the whole time i guess you are fucked” could derail everything and would need to serve a purpose.
As i said earlier, if you want resources to matter you need to hack the game.