In order to improve your websites SEO it is a good practice for each page to have a good quantity of 'real' text. When google see's (crawls) your webpage it see's all the code and all the content, if there is much more code than content it will appear like that page is not very informative for users.
It is recommended to have over 200 meaningful words per page, to help give it some weight and value to users.
Of coarse, this is not always the case, depending upon the purpose of the website and the specific purpose of that particular webpage, it could be a showcase where visual design is at the forefront and a wall of text is the lowest priority when your trying to look good (think like an art gallery here, a large picture and a small placard).
I hope this gives you an insight and provides value to take away and integrate on your own website, you've probably heard it before but in certain aspects of design, content is key.