It's a shame that the old Elite variables were not maintained e.g. 1g of precious gemstones, 1kg of gold/silver etc, 1t of grain. There's no reason why this can't be implemented, and no reason why scoopables have to use 1t of cargo space if they are merely data storage devices.
Maybe the devs will look into this soon?
I don't know... It kind of makes sense to have everything in standardized containers. Like the containers on a boat. They're all the same and it makes the job much simpler for everyone.
Also, If there was 1g of precious gemstones floating around in space, I don't think you'd be able to even see it, let alone scoop it effectively.
Maybe when we have the walking module they could enable us to get out of the ship and take individual things out of the canisters. But then it would also make sense to have them locked for security reasons, so..
Edit: When I think about it, since they have the same volume, cargo canisters should all take the same cargo space but have different weight. Ships would then have maximum cargo space instead of maximum cargo weight. This way, if you fly with 100 units of tea, your ship would be a lot lighter than if you flew with 100 units of gold.