Paul Boag, in his article Semantic code: What? Why? How? (http://boagworld.com/dev/semantic-code-what-why-how/) wrote:
HTML was originally intended as a means of describing the content of a document, not as a means to make it appear visually pleasing.
Unlike traditional content outlets such as newspapers or magazines, which are apparently intended for humans, the Web is read both by humans and machines such as search engines and screen readers that help visually impaired people navigate websites. So making our website structure semantic is really encouraged. Semantic markup allows these machines to understand the content better and also makes the content more accessible in different formats.
On that account, ...