The user’s search intent and behavior is different on mobile and desktop. Mobile web platform has several constraints with respect to content, interface and technicalities.
On the desktop, searchers usually enjoy a good Internet connection. Desktop searches can have long tailed, multiple and unique keywords. However in mobile, there are shorter keywords and it will remain so until voice search becomes popular.
Also, the keywords that help you rank for the desktop site will not give you better rankings for the mobile. A mobile site should have a clear and concise call-to-action. The page should be free from clutter and users shouldn’t be zooming the pages to read the content.
A mobile site should load faster. Google recommends a responsive site for an optimum user-friendly experience, but that is not always possible and users opt for a separate version for the mobile.
Website owners must make sure to test if their shopping carts and checkouts are working properly. This will ensure improved mobile conversions.
Mobile SEO is the need of the hour for local businesses as a user can easily find the stores, which are otherwise hard to dig up in the desktops.
To sum it up, mobile has a different ecosystem than the desktop. You should optimize the site considering the above factors because modern SEO is all about turning traffic into ROI and brand credibility!