Balance is key
It is true that the primary goal of alt text is to provide assistance for the impaired and for screen readers. The examples provided in this piece are best practices for leveraging SEO for your images, therefore, the key for you as a developer or stakeholder in your web development is to strike a balance between what is right for your users, and your customer requirements, and then apply what you can in the way of SEO. The only real "required by law" 508 compliance in the US is imposed for government sponsored web sites, i.e. *.gov, and I can tell you that it is a daily struggle for getting them to 100% compliance with every pixel on the page. Have you ever had the task of tagging a 38+ page PDF with graphics on every page for 508 compliance?
