Free sites like pixabay and unsplash are terrible for the photography industry. If someone wants to use a photo then they should be willing to pay for it, especially when it will make them money. If you have photos you think people would want, then definitely don't hand them out for free. It makes the public think that any photo they find online is free to use. Depending on the use of the image, some can be worth thousands of dollars, which you may be handing over for nothing...