it facilitates a wedge between the haves and have nots
In an environment where prices are falling (even if wages fall to match), any money you were able to save previously is now able to buy more things. This helps the haves and the have nots.
you can sit on some or all of your deflationary currency and wait for it to appreciate then you will receive more value without contributing anything.
If you "sit" on your money, you are forgoing consumption so that others may. You are also decreasing the supply of currency, increasing it's price. This raises the purchasing power of all consumers.
If the amount you earn is around what it costs you to survive, you stand almost no chance of ever striking it rich.
The goal of an economy is not to strike it rich. It's to first survive and second better your life. If the price of the things you need to survive goes down, you can save more money. Wages are sticky, so it's not likely that your income will fall with your expenses.
people do not act rationally
Aha! The crux! You think that in order to act rationally, someone must act rationally
by your standards. As Mises says:
Human action is necessarily always rational. The term 'rational action' is therefore pleonastic and must be rejected as such. When applied to the ultimate ends of action, the terms rational and irrational are inappropriate and meaningless. The ultimate end of action is always the satisfaction of some desires of the acting man.
When applied to the means chosen for the attainment of ends, the terms rational and irrational imply a judgment about the expediency and adequacy of the procedure employed … It is a fact that human reason is not infallible and that man very often errs in selecting and applying means. An action unsuited to the end sought falls short of expectation. It is contrary to purpose, but it is rational, i.e., the outcome of a reasonable — although faulty — deliberation and an attempt — although an ineffectual attempt — to attain a definite goal.