There's a slippery slope between "I saved hard and I don't want to lose the money I was recommended to invest in the stockmarket" and "I have a billion dollars in stock and I want to remain completely whole".
It is possible to achieve the first without the second. You can have federal insurance (like FDIC/SIPC) that fades out rather than has a strict cutoff (you get 100% of the first 100k, 80% of the next 400k etc etc).
There's some boundary where you "should" have been sophisticated and deserve to lose some money (probably near the point where you have a high end accountant look for deductions or are an accredited investor).
Yes, this is "unfair" to people who had very high paying jobs. But it's easy to argue that the current tax code is also "unfair". It's a question of "how unfair, and unfair to whom" not "we need this to be completely fair / preserve the status quo".