You absolutely can build 1000MB storage, literally almost all SSDs to my knowledge use SI units for storage (meaning 1TB = 1000GB). E.g. here, first link I found https://www.crucial.com/ssd/t705/CT2000T705SSD5
under footnote 6. 1 GB = 1 billion bytes
Nowadays most programmers don’t need to care about working with bits directly. And in general, it’s much better if the system is aligned with literally every other measurement unit in meaning. I also think it’s oftentimes deceiving exactly because it’s so close to 1000 that you just behave like it is, untill it actually starts making a difference at larger scales.
I think that for most people in 99% of usecases it would be better for MB to actually mean mega, and for the 1% you can clarify with MiB that it’s 1024.