It’s not a dumb question. There’s a technical reason behind it.
Computers use binary, which works naturally with powers of 2:
8 → 16 → 32 → 64 → 128 → 256 → 512 → 1,024.
Each step doubles the number of possible storage units, making memory chips and storage architectures easier to design and organize.
Could manufacturers make a 150GB or 300GB drive? Absolutely. There’s no rule against it.
But standard capacities based on powers of 2 are convenient for designing memory systems, while manufacturing economics, chip configurations, and product segmentation also influence what gets sold.
So it’s engineering first, with a bit of marketing layered on top.