Oh. fuck. no. Not even close.
If you paint something, that copyright is yours.
If you sell the painting, the copyright is still yours - you just sell the original piece out. They can sell the piece to someone else, but they can't duplicate the work unless given permission.
You as the artist still retain rights to the image: sell prints, tshirts, etc.
There has been an active copyright war between artists and companies because companies are actively stealing artwork and claiming they own the rights to it.
How fair is it for you to spend hundreds of hours on artwork, and then someone online comes along and sells it on tshirts and prints and tells YOU that you have no right to any of the profit generated? It's completely fucked.
The upside of sites like CGHUB and Deviantart is networking and exposure, but a lot of times people steal the artwork and sell it. If not online, in a local market. Some people even steal or re-appropriate other people's work into their portfolio.
It's fucking disgusting.
