Investing isn't for the rich only, sure they have some first-hand info where or whom to invest. But for most people are still learning and starting from scratch on how or when to invest. Investing is free for all ages as long as you have that guts and knowleldge.
Once you start investing, be ready to embrace the ups and downs on the road but make sure it's an asset that will worth something in the near future.
I agree with you, investing is for everybody who is willing to invest the time and learn and is saving money to do so. What the rich people can teach is us that we need investing to become rich, and once we are rich we need to keep investing to stay rich. Leaving all the money in an savings account is not an option. The same goes for just saving money in an savings account, we won't get enough interest to cover the inflation rate at the moment. The only real way is to start investing.