That's not just an Apple thing though. Google does the same thing. Dropbox only offers 2TB plan. OneDrive is just as expensive but offers 1TB.
They are all counting on you not using all of that space in the 2TB plan. So the avg user is subsidizing the usage of some small fraction of power users. They don't want to offer pay-per-use pricing plans because then they would have to increase the price ($/GB/month) to keep their existing margins.
They are all counting on you not using all of that space in the 2TB plan. So the avg user is subsidizing the usage of some small fraction of power users. They don't want to offer pay-per-use pricing plans because then they would have to increase the price ($/GB/month) to keep their existing margins.