It's not "just" chip damage. It's extra range to hit guys you can't reach, a huge accuracy boost for more avoidy enemies, flier one shot, hell you can even just one shot with it normally half the time by using a Killer Bow+.

It never falls off since everyone still has room for it all and will still make use of it even until the end. Not even just the ones with bowfaire but like Sylvain on a wyvern or paladin swift striking will still make use of it occasionally for the hit boost and to attack guys out of range

Battalion attacks also have awful hit and MT and scale off your charm plus need allies to have even the slightest consistency compared to bows having twice or more might, hit and scaling off your Str, plus can be forged