This is a good point. If your mental image of your character is a hulking slab of beef wrapped in plate armor, encumbrance isn't that much of an issue for you; most high-Strength characters can carry way more stuff than they need to.
If you want to play a sneaky, sly, artful dodger who isn't strong, but agile, encumbrance is a big deal, and interferes with what you want to do, since you have to carefully manage your inventory.
Now, obviously, Dexterity-focused characters have lots of advantages, so having a tradeoff is far from bad, but the tradeoff here is "you want Dexterity high? You get to do math and sometimes can't carry treasure."
You shouldn't balance mechanics by making them onerous to use- if you don't want low-Strength characters in the game, just ban them, lol.
Of course, realistically, what usually happens is that the party's strong guy carries around everything the other characters can't, and that's generally the end of worrying about encumbrance.