Warum? Deshalb…

• Using a single URL for a piece of content makes it easier for your users to interact with, share, and link to your content, and a single URL for the content helps Google’s algorithms assign the indexing properties for the content.
• No redirection is needed for users to get to the device-optimized view, which reduces loading time. Also, user-agent-based redirection is error-prone and can degrade your site’s user experience (see “Pitfalls when detecting user-agents” section for details).
• Responsive web design saves resources for both your site and Google’s crawlers. For responsive web design pages, any Googlebot user-agents needs to crawl your pages once, as opposed to crawling multiple times with different user-agents, to retrieve your content. This improvement in crawling efficiency can indirectly help Google index more of the site’s contents and keep it appropriately fresh.

Link zum Orginalartikel: Google recommends responsive design!