Well, like I was saying, is the bow the best grappling hook available? If not, it'd make more sense to have a grappling hook to pull walkways and such. Is it the best silenced weapon available? Is it better to retrieve 20 arrows or bring an extra magazine? What takes up more space than a big giant compound bow? It's not the practical option, and it would not be wise to try and sell it as though it were, because that would call for poor story writing. They need to write another story where Lara is forced to use a bow.
And while they could make Lara into Green Arrow/Hawkeye, it kinda negates the very thematic arc given to Lara's acquisition and use of the iconic dual pistols in the first game.
They already did it in the first. With that game, we can see how pratical the bow can be. Like I said before, it can be more hi-tech. It can be a kind of arrow with a panel in the middle that can expand and retrieve its "arms". This way, she could place it in her belt. I'd say it is better to retrieve 20 arrows (if it is within her reach)
and bring an extra magazine. The thing is, she can't retrieve the lost bullets once she is all out of it and, when she is in extreme conditions where more ammo or guns is nowhere in sigh, then the arrows are the best option. This happened in the first game. It is pratical because she can avoid carrying multiple devices, because she can retrieve arrows, because it is silent, because it can offer more attributes that my imagination can think of right now and, besides all, it can serve as a melee weapon too. So, yes, it is the best grappling hook available, because it can do more. It is the best silenced weapon, because you can retrieve its "ammo". What takes less space than a grappling hook, melee weapons, diverse guns, many magazines and other devices and resources? A bow that can become portable.
I disagree with your view that this is poor story writing, because she is familiar with the bow. Green Arrow/Hawkeye, with the super precise aim that they have, could also use guns, but they're familiar with the bow and its multiple uses. They could also have another device for the grappling, but why do that if the bow offers the same and more? We got Lara at the end with the dual guns, but she is more familiar and trained with the bow by the end of the game, so it is only natural that she carries an upgraded version of it for her next unknown adventures.
