So if I spend $5000 on groceries because I'm eating wagyu steak and lobster everyday, is that a fair "expense" too? You might retort that's obviously a luxury and there should be some baseline that's tax free, but then you're just describing the standard deduction.
>but as long as the value of investment is positive, that is, outpacing inflation, it makes zero sense to let your money languish in a Scrooge McDuck pile rather than get some value out of it.
...or they take their money elsewhere instead.