Inventory Space and Data transfer limitations

[Ardox]

And yet having 100 fishing baits that need data transfer does not matter?

I'm confused and fail to see what you mean.

I agree the number of baits is absurd and we'd need a proper tackle box, but even if there was a tackle box, it wouldn't change the underlying problem: It doesn't matter much what is in the inventory slots. Their reason is that there's a lot of data to transfert. When you do world visit or you go in a instance, they need to move 175 slots of regular inventory + 443(ish) slots of armory inventory + 13 gear slots + (however many) slots for character options (race, clan, hairstyle, etc.) + anything I missed and/or forgot about.

This I agree with. Even with a full quest log, would we really utilize that much space?

Actually it's good it never totally fills up since it would make progression in a quest impossible if the bag is full. I tend to always refresh WT, the singing cluster quest, CT raid quests, hunt marks, so mine is always half-ish full. Yes i can throw stuff out, but I prefer not having to need to.

[Niwashi]

When you do world visit or you go in a instance, they need to move 175 slots of regular inventory + ... [ etc. ]

The main issue isn't when you're moving to a different world or instance server. You do that only occasionally, so the servers are only dealing with it for a few characters at a time.

The bigger issue is backups. Every few seconds that you're logged in, all volatile data about your character --which includes everything in your main inventory and armory chest-- gets copied to SE's backup servers. Multiply that by every character that's online, and it's a lot of data to transfer every couple seconds or so.

That's why systems like retainer inventory are easier on the servers than your main inventory is. Since your retainers' inventory can only change when you summon them, the game can trust that the previous backup of it is still current so long as you haven't summoned them since then. That means there's a lot fewer times that that data needs to be backed up.

(It's likely that the same holds true of saddlebags, that they're only backed up if you've opened them since the last backup. At least that'd be the logical way to program it. But the only time I've heard about it directly from SE was an interview from years ago, before saddlebags were added to the game.)