Insider trading is probably the worst possible crime committed under the euphenism of "white collar" crime.
It only works if you are an insider, hence the term. If you are a general investor in the stock market, you are already at the mercy of inside investors. If insider trading were made legal, no-one could trust the system and the stock market could no longer function properly.
The stock market only works if everyone is confident that they have the same information as everyone else, at the same time.