you also have to remember, this game (14) is two weeks old. did you have 400 slots of inventory space two weeks into 11? no, nobody did. so when you compare beginning 14 to beginning 11, 14 has a default of much more inventory space.
But again, that is offset by the increase in loot. Just from fighting marmots you will end up with several inventory slots taken up by walnuts, furs, and moko grass. And their +1 +2 +3 varieties.
There's not much in the way of vendor trash here. Virtually every item has some kind of use. With the armoury system built around players to switch between the classes, that encourages players to hang onto items since they can use them.
But as it stands right now, you don't have enough room to do that. You have to hang onto the useful items, tools/weapons, and alternative gear sets.
Assume for a moment that you've taken on one class from each discipline. If you want to be properly geared for each of those jobs, than ignoring jewelry, that means you will potentially be carrying...
Which comes out to a total of 30 inventory slots already taken up. That's assuming you aren't a DoW class that uses ammunition or a shield, and that you have no jewelry. You have an additional 2 slots taken up by your undershirt/shorts, so now you're up to 32 slots.
Supposing your DoH class is miner, you're going to be bringing up copper and tin ore fairly regularly, as well as the rarer ores like yellow copper ore, limonite, and iron. Ignoring everything else that you can mine or quarry, if you dig up those 5 types of ores and only two of the +1 +2 +3 varieties, that would be 3 slots for each type of ore, making 15 in total. Now you're up to 47 slots. That isn't even counting multiple stacks.
As you start crafting, you will end up creating materials that you don't immediately use up. For example, if you're a blacksmith you will create 12 copper buckles at a time. All of these extra components will probably be useful at some point, so you wont want to throw them away. That's more space gone.
That's over half your inventory space gone before you even get a single piece of loot from mobs. It's also before you have to take on another DoH class to create particular components needed for your main DoH. Which would mean you have to start carrying the tools, materials, and components from that
class as well.
What I'm trying to illustrate is how quickly you run out of space here. It wasn't the same in XI, so you can't use that as an example. The armoury system encourages players to switch between classes, but the current item/loot system prevents that from being an option.