This is actually a discussion that I have had in the past.
Generally speaking, what you are describing with all passive holders loosing 10%, rather than all active stakers earning 10% is economically the same, and a deflationary model is certainly preferable for a number of reasons, not least of which would be reporting of taxes / income. So you are certainly coming from a place which makes sense.
However, from a technical perspective, designing such a system is much more complex and has much more overhead.
For example: All changes on change need to be triggered by some internal or external action. We cannot have Polkadot automatically decrease the balance of all passive users (which is a large majority of the token holders). Such an action would be extremely resource heavy. Imagine the on-chain costs of updating 1M users account balances, and how that will increase as more DOT holders come.
Fortunately, for staking with rewards, a small minority of stakers are already incentivized to make on-chain transactions to claim their rewards, paying for and triggering all the on-chain logic.
Also imagine from the user experience perspective: you transferred some balance to a cold wallet, and then a year later you come back and 10% of it is gone, without you taking any action. Imagine you start with just 1 DOT, then you go below the existential deposit, and your account gets deleted!
Finally, the inflationary model is one which supports ideas like the treasury. As your graph shows, some amount of the inflation goes to the treasury to be spent on improving the network. Discussion here is actually trying to discuss how to ensure that treasury has a consistent income from inflation.
With your idea, I guess we could simply move funds from users into the treasury account, and have that be the “deflationary” pressure, but again, such a process unfortunately just doesn’t scale.
However, that is not the end of the discussion. While it is not practical to me to create a deflationary system, there are other kinds of economic primitives which can provide similar kinds of behaviors as a deflationary model, for example Non-Interactive Staking.
In summary, I think the inflation system implemented today is basically a deflationary system to passive token holders. I think it is just all perspective, and the underlying economics is mostly the same. I think it would not be crazy for Polkadot to have used the deflationary model, except that it is technically non-feasible.