Not everyone agrees that insider trading is bad. The United States SEC and DOJ are the only one that prosecutes it. When they do prosecute it, they have the stiffest penalties globally. And they only do it some of the times.
The laws deterring insider trading are - as you observed - to give people CONFIDENCE that they aren't going to get screwed. Confident to gamble in the markets, because they'll be "fair".
Stock markets aren't that popular around the world partly because investors don't feel like they won't get screwed over. Liquidity really does suck in most national and regional markets!
Its all a game of confidence man.
In many places, and yes you still see this in the US as well, the driving perception is that if you have attained a place in society to have privileged information, then you have the privilege of making money from it.