Why are we so secretive about our finances?

M. asked me: Why do we have to be so secretive with our friends or family members about our finances?

When we are secretive, it means we feel like we have to hide something. But why would we hide? 

Generally, consciously or subconsciously, we sort all our personal contacts based on 2 criteria: usefulness and potential danger.

 
Here are the examples: 

How useful or dangerous someone is, is defined by the resources the target person possesses. 

Money is  one of the main resources. 
Let's take an interaction between two people. If the level of wealth is about the same, sharing the information about it doesn't appear very dangerous. 
If there is a dis-balance and one site has significantly less resources, the sharing may have consequences. 

It might be that the person with less resources decides to aggressively take some of yours. Or the person might put you into a situation that you will feel that you have to share those resources even if you natural inclination is not to share. It can be done trough manipulations like making you feel guilty. "Just because you have more you have to share, it doesn't matter that you worked harder to get there".    
A normal good friendship is based on balance. 

I am not talking about abnormal friendships which are based on secondary psychological gains. For example someone keeps a poor looser friend and constantly helps him financially. The secondary gain in this case is to feel as a "better person" and to pay off the moral guilt. The moral guilt is usually brought on by abusive family members, or religious businesses.

The normal friendship without secondary gains is balanced. The balance makes the relationship harmless because there is no danger of appearing significantly weaker or stronger. The possibility of being manipulated out of some of your resources is very small. 

We choose our friends. 
We don't choose our family. The resources in the family will be unevenly distributed. If you feel the strong social pressure to keep in contact with your relatives, you will constantly feel some of the dis-balance. 

For example you have an abusive mother whose finances are not in a good shape. In the square above she falls into category of useless and dangerous but you can't stop the socially obligated contact. By hiding the information about your financial recourse you protect yourself. 

If you have a brother ho is not abusive but is not in a good financial situation and he is not asking you for money, his category might be useless and not dangerous. Here some people can feel guilty for their own success and feel that they have to even out the situation, even though a situation like that can never be evened out. 
Some would offer money, some would hide the information about the finances. Some may even pretend that they also have financial troubles, to make the financial situation less clear.  Lying about your finances is another way of protection. What protection works best is situational. Sometimes it is better just not to talk, sometimes it is better to lie. In a contact with an abusive/manipulative person lying is completely justified. As soon as the other site starts using unfair methods, you are released from the rule of playing fair.  

I summary, it will always be difficult to have a relaxed connection if there is a dis-balance of resources. 

If you accept that it is normal to protect yourself and accept the fact that you don't have to play fair with manipulative people, it will make your life easier.