It's called Keeping Content Relevant.
The last F2P game I played, you only had an inventory of 15 slots and a bank of 20? Shared bank of 10. With premium, all slots were doubled. 30 inventory, 40 bank, 20 shared. More slots had to be bought in increments of 5 I believe for $3 each That game was DC Universe Online but I quit that back in late 2014. For FFXIV
Here I get to have 140 inventory, 350 retainer slots, 40 potential slots via sale slots, 150 FC chest slots, 520 armor slots and all for no extra fees. Multiply that 140 and 520 by 8 because of alts. Then there are the mail slots!