Why is retainer STORAGE not buy once have forever?

[Titor]

I can understand keeping the selling and venture functionality to paid retainers if really necessary, since those are more server load and all that, but the actual storage itself.

The storage is kept forever, if you buy the max amount of retainers the day before your sub ends, fill them all up with some vendor gear, then never renew your retainers again, those items and that data is stored. So this cannot be a matter of server limitations, since the data is there, it will always be there, but will be inaccessible to you until you renew then. Even if you never renew them again, that data and those items will still be there.

It seems like an unnecessary pay gate for using the storage itself. If they want to charge for marketboard space or ventures fine (since I guess that is technically extra data that is not stored when they are inactive). But the inventory part-- that should be buy once have forever, since it is still there anyway.