Everyone is taking pictures by some device or another. Everyone is posting those photos on a media site. Facebook is a big one and I do use it mostly to share with family and friends. Also to let others know what I am up to. I do post some things from time to time. However, posting a quality photo to the sharing sites may not be the best place if you are trying to show case something. They resize and do some other things and if you spent time processing it the photo will not be as good as when you post it. Another reason I like media sites is reading the groups I belong to. Sometimes I learn what not to do. I often post a link to the photo from my web site in lieu of posting the actual photo because the photo looks so much better at the website than on the media sites. It also allows me to link many photos at once instead of having them posted multiple times. If you post it on Facebook anyone can download it. They can screen print it from any site but the quality of a screen print is not as good as getting a free download. There are many reasons to post the link. It also helps with driving traffic to your website and increase rankings. The higher the rankings the closer to the top of the search engine when someone searches your subject matter. More Traffic more opportunity to sell photography or any other service you want to offer. I don't take photos to sell but I do want to show them at their best. If I do sell something it's a bonus. I used to build and maintain my own site and have since bought into one of the sell your photo sites. You can customize them enough to not look like a stock site. No programing and a shopping cart is available based on the plan you buy into. They can take care of everything from taking payment, printing and shipping wherever you want. I tried Smugmug first but found it difficult to use. It's been awhile and all the sites have made improvements over time and no one site will be perfect. Do your research if you go that way. Most people can't build a website and paying for it can be costly. Also you can't be out doing better photography if you are managing a website. If you want to sell it gets more complicated. I prefer to shoot more.
If you are taking better photography why not take a little more effort and show it at its best. Show only your best. After all isn't that what its all about.