Both have different reasons but with similar purpose which is to earn more. It will always depend on your purpose. Others maybe afraid to gamble then they just do investments because they are comfortable with that. Some may do gambling for fun and get instant or higher returns. Mostly they do both to have a long term and short term returns. Whatever reasons it maybe, for me gambling is part of investments. We took the risks in both activities.
The statement made by op sounds like so real but actually it's misleading, investment for sure should be done with careful analysis, those people who pick random investment are the one who have no idea about the legitimate business, making money properly aren't like that. You wouldn't find a successful way with it.