Imagine an uncompressed image large enough to fill the card, at the size where you can make out every pixel, like 1mm pitch. Then imagine how small each pixel would be if you shrank it down to the size of the chip.
For 1 bit monochrome, 1TB is 2828427 x 2828427. At 1mm pitch, that's is 3 square miles. Imagine shrinking that down to 5mm.
(Edit in response to replies. This example is purposefully simplistic to demonstrate the point about shrinking pixels. A real photo wouldn't be monochrome, or 1-bit depth, or have a dot pitch of 1mm, or be uncompressed, or, for that matter, be 3 square miles big. I mean, who has that much ink?)
Edit 2: For a 2MB Compact Flash card from 1990s the equivalent is 16 square metres. That's still a lot of pixels to squeeze into such a tiny package.