Banks have rules on what they can use the money in your savings account for. They have government backed insurance.
Regular stocks are also heavily regulated. Financial reporting requirements, disclosures, auditing, etc.
Why does all this regulation exist? Because people we getting screwed over, and it was bad enough the government had to step in.
The mortgage industry was not heavily regulated enough, and what happened there? A large financial crash. And who got bailed out? The banks, many of whom were somewhat complicit and profiting off the situation.
Who didn't get bailed out? The little people.
This is still happening now. Most hedge funds, high frequency trading, the lure of day trading, and may other schemes exist to siphon off money from regular people.
Think for a minute about the hedge fund manager who gets tens of millions in bonuses. Where does that money come from? Ultimately the companies and other investors. That money could have gone into higher wages for the workers, but instead is being funneled to a few elites.
Since ancient times, the powerful have sought to retain and grow their own power. They use whatever means are available to them. It can be the use of force, but things have gotten more sophisticated.