Great Hunt!
I'm no artist but I do have an artist/concept illustrator friend and I think the main problem for digital artists are really copyright infringement.
I've taken a look at the site and while they might have disabled the right click option to not save the images on the site, one could just easily "inspect element" or take a screenshot to steal the images.
Still a good platform for artists though to earn extra money. XD Great Hunt!
Maybe it's one of their ways to prevent theft of digital works, thank you for visiting.