Why Apple does not offer other tiers of cloud storage ie 300GB, 500GB, 700GB and why jump from 200GB to 2TB???

Isn't the motto of cloud to save cost and not lock people into unnecessary spend with higher fixed tiers of storage? Why not offer all tiers at 50GB or 100GB increments between 100GB to 2TB at linear scale or charge only for what is in use by users?

If Apple does offer that people will use the iCloud storage lot more and Apple make lot more money in the end. To avoid going to higher tiers, I am forced to clean up lot of stuff, whereas, if there was intermediate storage tiers or pay-as-you-use offered, it would be much better solution!