Can you think of any reasons why someone would want to do that? My only thought is that people would use that ranking, that position on a search page, as a springboard to lead people to their main site. What do you think?
It could bring more eyes to your portfolio. I think most people do it though because they also run a blog and are looking to bring people to their website for advertising and affiliate money.
Driving traffics is always a good way to promote your stuff I suppose? But I wonder how do people get their images ranked high on Google? Like how do they make it?
Driving traffic to your website is an excellent way to advertise, but it may not be as effective as it was a few years back (I stand corrected). Linking your site to all your social media profiles can be a great way to make a name.
Google changes its algorithm in a regular sporadic fashion, and the last I heard is that text will rank higher when a picture accompanies it. Having that same picture rank high in G Images would help as well.
Ranking your images on Google is a way to get your website up in the Google search results. Other than that, I don't see any reason why anyone would want to do that.