There needs to be an in-game Bestiary with drop lists

[LibitIncarne]

1. At a markup, of course. My sorry self on Dynamis would not dream of paying the high price of raw materials on the MB.

2. Max rank for all zones is a significant investment of time that not everyone would be willing to commit to compared to just going to a zone and killing 50 quickly-respawning mobs, especially if they have other things they'd rather do in the game with their time. Some people have jobs, yeah?

3. This does not account for materials in previous expansions (which still have their uses), and again, there are other things people may want to use their bicolors on. I have probably spent several thousands of bicolors on mats when leveling my DoH jobs.

If the only reason for a Bestiary not existing is "the inconvenience of not having one is based", then I fail to see this argument have much ground.

1: You can World or even Data Center Travel to avoid paying the markup.
Example: Gargantua Hide is 1.5k Gil on Seraph. It is ~500 on Halicarnassus, and ~420 on most Primal/Aether servers.

2: This point is irrelevant considering that the monster drop materials are buyable on the same map as where they drop.

3: People don't just stop doing maps because they're from a past expansion. Achievement Hunters want all of the map clear titles, and FCs that do map nights want variety so they do maps of all expansions.
Bicolors farmed in Dawntrail Areas can be used on both Shadowbringers and Endwalker materials, and vice versa. Now you can farm materials from Shadowbringers while levelling in Yak T'el!

It would be a nice to have feature indeed, but because the drop rate for these items is way too low, there is no reason to hunt the monsters when you can just send a retainer.
You can kill 10 monsters and not get a single drop.

This isn't ARR where Ventures are actually worth something and you can get 7 fleece from a Karakul sometimes. The droprates are hilariously low, and it takes over 20 seconds to kill each monster. If you spend 5 minutes flying around the map and only manage to get 7 drops, it would have been better to invest your time in doing FATEs.
Each (Combat) Retainer you have, provided that they're levelled and geared, can bring back 15 of any item once an hour.