I'm a developer, and I've never used Bootstrap in my life, but my favorite aspect of Bootstrap is how it brings a sense of familiarity to the web. Why does every website need a unique look and feel? I'd rather not learn a new navigation or layout a hundred times each day. The internet is primarily about content, and Google should know that more than anyone. However, everyone tries to reinvent the wheel, and when I come across a Bootstrap site, it's somewhat comforting.

Don't get me wrong, creativity is important to some sites, and others are required to go outside of the box to reach their goals. However, they're the minority.