For me, the top ones to bubble up are
1. Shame
2. Embarrassment
3. Trying to shield children from difficulties
Same with shielding your children from difficulties; they are going to sense things, and their imagination will be worse than the reality. Tell them your problems, but do so in a way that conveys your confidence that you can overcome them. You are teaching them about life, which is really just a series of difficulties that you overcome.
To avoid financial information being compared between families. This already happens via secondary signals, like clothes and possessions, adding direct financial comparison makes the poison stronger.
A better way is to make a toy budget based on allowances.
Are you really going to teach tham that it's bad?
If they still believe in fairy tales, santa, etc. and believe that life ahead is a bed of roses, it's so easy to fall off the wagon.
I doubt people make a rational decision not to do it; they just avoid it because it makes them feel bad.
We would often have family budget meetings, where we could all make our cases as to why we should spend more on one thing than another. Of course, my parents always had the final say, but they would listen to me and explain why they made the decisions they did (sorry, your sister's braces are a higher priority than your PowerWheel car).
Because of this early exposure, I never had the same financial problems my friends did, even when I was a very poor student and recent grad. I never accumulated credit card debt, nor did I buy a car that was too expensive for my budget. I always saved for retirement, starting with my first job. Budgeting and money management is just second nature to me.
I can't think of a single argument as to why you would want to hide this valuable learning experience from your kids.