Hussar
Legend
I think this, right here, is the basic issue. This is something that is quite common IME. It's not that players don't care. It's that they will never care as much as you do about your setting. If you're DMing, you're thinking about this stuff all the time. When you design a scenario, the setting is something you're drawing on a lot of the time and you're probably spending some mental effort trying to make whatever scenario you're building fit within the campaign.And you need to recognize that there are players--quite a lot of them IME--who don't want to seriously deal with any setting's lore. And no, not playing with such players is not a functional option for everyone.
IOW, a DM won't deliberately (most of the time) make material that is totally divorced from the campaign. That's kinda that point of a campaign. You are making material for that campaign which means you are making material for that world. As a player, you never have that level of involvement in the setting. Not in D&D at least. Which means that the players are automatically a step or two removed from the setting.
And we see that remove in the characters they bring to the campaign.