The stock market opens the investment business to the small player.
There is a huge advantage to the large investor , but without the stock market the small investor would be totally shut out.
When you buy a few shares , often the seller is harvesting a profit , or if taking a loss is harvesting what he can.
The big investors sell sometimes just so that they can buy something new. Since money is very fungable in the stock market a big buyer is very likly to trade holdings old for new.
A diving stock market DIRECTLY removes value from the pool of investment that funds old and new investment, in tight money times it is hard to get a new business started and hard to get an old business expanded.
It isn't because anyone likes it that way, and it isn't because anyone anyone hates it that way, proper regulation prevents cheating , not the flow of tides .