To give out stuff for free is a great marketing strategy. Not only it attracts users to what you’re doing but it also validates that you can create something others want.
If you’re a blogger, trying to sell a book or get users sign up for your product, you will want to publish free high quality content which is similar to what you offer. Some of the readers who will like your free content will want to read more and will pay for what you offer.
If you are selling a software product, create a free version of what you’re doing first and additional paid features. If no one uses the free version, then maybe it means what you’re building is not needed or you couldn’t get it in front of the right audience yet. You need to fix that before trying to figure out why no one pays.
Of course it’s not guaranteed that the free users will purchase your paid plans, but at least you will have something to improve upon. Even if you are not able to monetize your free product, you will be able to at least direct that traffic to another product with a better conversion rate.