Actually, you're completely allowed to conceal facts. I've given a number of situations where this is true. I've even given situations where the law specifically protects secrets.
There's a powerful difference between "nice to have"s and "legally required to have"s. You keep using the word right, but a right is a very powerful and dangerous thing, and contrary to your belief, it isn't something that has basis in law.
For example, I'm not entitled to know the recipe and process for making coca cola. It is, in fact, a protected trade secret. Before buying a coke, or indeed before buying stock in coke, that information would be unquestionably relevant (to determining the value of your purchase, but just because it's nice to have, doesn't mean coca cola is ever required to tell you. You do NOT have a right to the information.
The entire stock market is based on the idea of getting the scoop on others who don't have the same information you do. In some cases it is restricted(insider trading, for example), but in most cases, the Warren Buffets of the world are rewarded, not punished, for buying securities at the wrong price and selling them at another much higher price. There is no basis to assume by selling a stock to Warren Buffett, you have a RIGHT to know the reasons he's buying the stock, which would certainly be an unquestionably relevant piece of information. The point of the stock exchange is to avoid an equal exchange of value, to try to get something that is actually much more valuable than the person selling it to you thinks it is.