Yes that's what a retainer is, an inventory that's not accessible in high server load contexts.
We can't have more retainers, or similar styled ancillary inventories, without uprooting the subscription model and costing SE a load of income.
It's not something that's going to change, and you can call it "greedy" all you like, youre not wrong, but there's nothing they can do about it, they're not about to reduce their income are they? Would you take a pay cut to benefit your customers/service users in your job? Maybe if your customers would leave otherwise... but that's not going to happen here.